Go

Create a high-performance HTTP benchmarking tool in Go. Implement concurrent request generation with configurable thread count. Add detailed statistics including latency, throughput, and error rates. Include support for HTTP/1.1, HTTP/2, and HTTP/3. Implement custom header and cookie management. Add request templating for dynamic content. Include response validation with regex and status code checking. Implement TLS configuration with certificate validation options. Add load profile configuration with ramp-up and steady-state phases. Include detailed reporting with percentiles and histograms. Implement distributed testing mode for high-load scenarios.

Build a high-performance file system indexer and search tool in Go. Implement recursive directory traversal with configurable depth. Add file metadata extraction including size, dates, and permissions. Include content indexing with optional full-text search. Implement advanced query syntax with boolean operators and wildcards. Add incremental indexing for performance. Include export functionality in JSON and CSV formats. Implement search result highlighting. Add duplicate file detection using checksums. Include performance statistics and progress reporting. Implement concurrent processing for multi-core utilization.

---
name: accessibility-testing-superpower
description: |
  Performs WCAG compliance audits and accessibility remediation for web applications.
  Use when: 1) Auditing UI for WCAG 2.1/2.2 compliance 2) Fixing screen reader or keyboard navigation issues 3) Implementing ARIA patterns correctly 4) Reviewing color contrast and visual accessibility 5) Creating accessible forms or interactive components
---

# Accessibility Testing Workflow

## Configuration

- **WCAG Level**: AA
- **Component Under Test**: Page
- **Compliance Standard**: WCAG 2.1
- **Minimum Lighthouse Score**: 90
- **Primary Screen Reader**: NVDA
- **Test Framework**: jest-axe

## Audit Decision Tree

```
Accessibility request received
|
+-- New component/page?
|   +-- Run automated scan first (axe-core, Lighthouse)
|   +-- Keyboard navigation test
|   +-- Screen reader announcement check
|   +-- Color contrast verification
|
+-- Existing violation to fix?
|   +-- Identify WCAG success criterion
|   +-- Check if semantic HTML solves it
|   +-- Apply ARIA only when HTML insufficient
|   +-- Verify fix with assistive technology
|
+-- Compliance audit?
    +-- Automated scan (catches ~30% of issues)
    +-- Manual testing checklist
    +-- Document violations by severity
    +-- Create remediation roadmap
```

## WCAG Quick Reference

### Severity Classification

| Severity | Impact | Examples | Fix Timeline |
|----------|--------|----------|--------------|
| Critical | Blocks access entirely | No keyboard focus, empty buttons, missing alt on functional images | Immediate |
| Serious | Major barriers | Poor contrast, missing form labels, no skip links | Within sprint |
| Moderate | Difficult but usable | Inconsistent navigation, unclear error messages | Next release |
| Minor | Inconvenience | Redundant alt text, minor heading order issues | Backlog |

### Common Violations and Fixes

**Missing accessible name**
```html
<!-- Violation -->
<button><svg>...</svg></button>

<!-- Fix: aria-label -->
<button aria-label="Close dialog"><svg>...</svg></button>

<!-- Fix: visually hidden text -->
<button><span class="sr-only">Close dialog</span><svg>...</svg></button>
```

**Form label association**
```html
<!-- Violation -->
<label>Email</label>
<input type="email">

<!-- Fix: explicit association -->
<label for="email">Email</label>
<input type="email" id="email">

<!-- Fix: implicit association -->
<label>Email <input type="email"></label>
```

**Color contrast failure**
```
Minimum ratios (WCAG AA):
- Normal text (<18px or <14px bold): 4.5:1
- Large text (>=18px or >=14px bold): 3:1
- UI components and graphics: 3:1

Tools: WebAIM Contrast Checker, browser DevTools
```

**Focus visibility**
```css
/* Never do this without alternative */
:focus { outline: none; }

/* Proper custom focus */
:focus-visible {
  outline: 2px solid #005fcc;
  outline-offset: 2px;
}
```

## ARIA Decision Framework

```
Need to convey information to assistive technology?
|
+-- Can semantic HTML do it?
|   +-- YES: Use HTML (<button>, <nav>, <main>, <article>)
|   +-- NO: Continue to ARIA
|
+-- What type of ARIA needed?
    +-- Role: What IS this element? (role="dialog", role="tab")
    +-- State: What condition? (aria-expanded, aria-checked)
    +-- Property: What relationship? (aria-labelledby, aria-describedby)
    +-- Live region: Dynamic content? (aria-live="polite")
```

### ARIA Patterns for Common Widgets

**Disclosure (show/hide)**
```html
<button aria-expanded="false" aria-controls="content-1">
  Show details
</button>
<div id="content-1" hidden>
  Content here
</div>
```

**Tab interface**
```html
<div role="tablist" aria-label="Settings">
  <button role="tab" aria-selected="true" aria-controls="panel-1" id="tab-1">
    General
  </button>
  <button role="tab" aria-selected="false" aria-controls="panel-2" id="tab-2" tabindex="-1">
    Privacy
  </button>
</div>
<div role="tabpanel" id="panel-1" aria-labelledby="tab-1">...</div>
<div role="tabpanel" id="panel-2" aria-labelledby="tab-2" hidden>...</div>
```

**Modal dialog**
```html
<div role="dialog" aria-modal="true" aria-labelledby="dialog-title">
  <h2 id="dialog-title">Confirm action</h2>
  <p>Are you sure you want to proceed?</p>
  <button>Cancel</button>
  <button>Confirm</button>
</div>
```

## Keyboard Navigation Checklist

```
[ ] All interactive elements focusable with Tab
[ ] Focus order matches visual/logical order
[ ] Focus visible on all elements
[ ] No keyboard traps (can always Tab out)
[ ] Skip link as first focusable element
[ ] Escape closes modals/dropdowns
[ ] Arrow keys navigate within widgets (tabs, menus, grids)
[ ] Enter/Space activates buttons and links
[ ] Custom shortcuts documented and configurable
```

### Focus Management Patterns

**Modal focus trap**
```javascript
// On modal open:
// 1. Save previously focused element
// 2. Move focus to first focusable in modal
// 3. Trap Tab within modal boundaries

// On modal close:
// 1. Return focus to saved element
```

**Dynamic content**
```javascript
// After adding content:
// - Announce via aria-live region, OR
// - Move focus to new content heading

// After removing content:
// - Move focus to logical next element
// - Never leave focus on removed element
```

## Screen Reader Testing

### Announcement Verification

| Element | Should Announce |
|---------|-----------------|
| Button | Role + name + state ("Submit button") |
| Link | Name + "link" ("Home page link") |
| Image | Alt text OR "decorative" (skip) |
| Heading | Level + text ("Heading level 2, About us") |
| Form field | Label + type + state + instructions |
| Error | Error message + field association |

### Testing Commands (Quick Reference)

**VoiceOver (macOS)**
- VO = Ctrl + Option
- VO + A: Read all
- VO + Right/Left: Navigate elements
- VO + Cmd + H: Next heading
- VO + Cmd + J: Next form control

**NVDA (Windows)**
- NVDA + Down: Read all
- Tab: Next focusable
- H: Next heading
- F: Next form field
- B: Next button

## Automated Testing Integration

### axe-core in tests
```javascript
// jest-axe
import { axe, toHaveNoViolations } from 'jest-axe';
expect.extend(toHaveNoViolations);

test('component is accessible', async () => {
  const { container } = render(<MyComponent />);
  const results = await axe(container);
  expect(results).toHaveNoViolations();
});
```

### Lighthouse CI threshold
```javascript
// lighthouserc.js
module.exports = {
  assertions: {
    'categories:accessibility': ['error', { minScore: 90 / 100 }],
  },
};
```

## Remediation Priority Matrix

```
Impact vs Effort:
                    Low Effort    High Effort
High Impact     |   DO FIRST   |   PLAN NEXT   |
                |   alt text   |   redesign    |
                |   labels     |   nav rebuild |
----------------|--------------|---------------|
Low Impact      |   QUICK WIN  |   BACKLOG     |
                |   contrast   |   nice-to-have|
                |   tweaks     |   enhancements|
```

## Verification Checklist

Before marking accessibility work complete:

```
Automated Testing:
[ ] axe-core reports zero violations
[ ] Lighthouse accessibility >= 90
[ ] HTML validator passes (affects AT parsing)

Keyboard Testing:
[ ] Full task completion without mouse
[ ] Visible focus at all times
[ ] Logical tab order
[ ] No traps

Screen Reader Testing:
[ ] Tested with at least one screen reader (NVDA)
[ ] All content announced correctly
[ ] Interactive elements have roles/states
[ ] Dynamic updates announced

Visual Testing:
[ ] Contrast ratios verified (4.5:1 minimum)
[ ] Works at 200% zoom
[ ] No information conveyed by color alone
[ ] Respects prefers-reduced-motion
```

# COMPREHENSIVE GO CODEBASE REVIEW

You are an expert Go code reviewer with 20+ years of experience in enterprise software development, security auditing, and performance optimization. Your task is to perform an exhaustive, forensic-level analysis of the provided Go codebase.

## REVIEW PHILOSOPHY
- Assume nothing is correct until proven otherwise
- Every line of code is a potential source of bugs
- Every dependency is a potential security risk
- Every function is a potential performance bottleneck
- Every goroutine is a potential deadlock or race condition
- Every error return is potentially mishandled

---

## 1. TYPE SYSTEM & INTERFACE ANALYSIS

### 1.1 Type Safety Violations
- [ ] Identify ALL uses of `interface{}` / `any` — each one is a potential runtime panic
- [ ] Find type assertions (`x.(Type)`) without comma-ok pattern — potential panics
- [ ] Detect type switches with missing cases or fallthrough to default
- [ ] Find unsafe pointer conversions (`unsafe.Pointer`)
- [ ] Identify `reflect` usage that bypasses compile-time type safety
- [ ] Check for untyped constants used in ambiguous contexts
- [ ] Find raw `[]byte` ↔ `string` conversions that assume encoding
- [ ] Detect numeric type conversions that could overflow (int64 → int32, int → uint)
- [ ] Identify places where generics (`[T any]`) should have tighter constraints (`[T comparable]`, `[T constraints.Ordered]`)
- [ ] Find `map` access without comma-ok pattern where zero value is meaningful

### 1.2 Interface Design Quality
- [ ] Find "fat" interfaces that violate Interface Segregation Principle (>3-5 methods)
- [ ] Identify interfaces defined at the implementation side (should be at consumer side)
- [ ] Detect interfaces that accept concrete types instead of interfaces
- [ ] Check for missing `io.Closer` interface implementation where cleanup is needed
- [ ] Find interfaces that embed too many other interfaces
- [ ] Identify missing `Stringer` (`String() string`) implementations for debug/log types
- [ ] Check for proper `error` interface implementations (custom error types)
- [ ] Find unexported interfaces that should be exported for extensibility
- [ ] Detect interfaces with methods that accept/return concrete types instead of interfaces
- [ ] Identify missing `MarshalJSON`/`UnmarshalJSON` for types with custom serialization needs

### 1.3 Struct Design Issues
- [ ] Find structs with exported fields that should have accessor methods
- [ ] Identify struct fields missing `json`, `yaml`, `db` tags
- [ ] Detect structs that are not safe for concurrent access but lack documentation
- [ ] Check for structs with padding issues (field ordering for memory alignment)
- [ ] Find embedded structs that expose unwanted methods
- [ ] Identify structs that should implement `sync.Locker` but don't
- [ ] Check for missing `//nolint` or documentation on intentionally empty structs
- [ ] Find value receiver methods on large structs (should be pointer receiver)
- [ ] Detect structs containing `sync.Mutex` passed by value (should be pointer or non-copyable)
- [ ] Identify missing struct validation methods (`Validate() error`)

### 1.4 Generic Type Issues (Go 1.18+)
- [ ] Find generic functions without proper constraints
- [ ] Identify generic type parameters that are never used
- [ ] Detect overly complex generic signatures that could be simplified
- [ ] Check for proper use of `comparable`, `constraints.Ordered` etc.
- [ ] Find places where generics are used but interfaces would suffice
- [ ] Identify type parameter constraints that are too broad (`any` where narrower works)

---

## 2. NIL / ZERO VALUE HANDLING

### 2.1 Nil Safety
- [ ] Find ALL places where nil pointer dereference could occur
- [ ] Identify nil slice/map operations that could panic (`map[key]` on nil map writes)
- [ ] Detect nil channel operations (send/receive on nil channel blocks forever)
- [ ] Find nil function/closure calls without checks
- [ ] Identify nil interface comparisons with subtle behavior (`error(nil) != nil`)
- [ ] Check for nil receiver methods that don't handle nil gracefully
- [ ] Find `*Type` return values without nil documentation
- [ ] Detect places where `new()` is used but `&Type{}` is clearer
- [ ] Identify typed nil interface issues (assigning `(*T)(nil)` to `error` interface)
- [ ] Check for nil slice vs empty slice inconsistencies (especially in JSON marshaling)

### 2.2 Zero Value Behavior
- [ ] Find structs where zero value is not usable (missing constructors/`New` functions)
- [ ] Identify maps used without `make()` initialization
- [ ] Detect channels used without `make()` initialization
- [ ] Find numeric zero values that should be checked (division by zero, slice indexing)
- [ ] Identify boolean zero values (`false`) in configs where explicit default needed
- [ ] Check for string zero values (`""`) confused with "not set"
- [ ] Find time.Time zero value issues (year 0001 instead of "not set")
- [ ] Detect `sync.WaitGroup` / `sync.Once` / `sync.Mutex` used before initialization
- [ ] Identify slice operations on zero-length slices without length checks

---

## 3. ERROR HANDLING ANALYSIS

### 3.1 Error Handling Patterns
- [ ] Find ALL places where errors are ignored (blank identifier `_` or no check)
- [ ] Identify `if err != nil` blocks that just `return err` without wrapping context
- [ ] Detect error wrapping without `%w` verb (breaks `errors.Is`/`errors.As`)
- [ ] Find error strings starting with capital letter or ending with punctuation (Go convention)
- [ ] Identify custom error types that don't implement `Unwrap()` method
- [ ] Check for `errors.Is()` / `errors.As()` instead of `==` comparison
- [ ] Find sentinel errors that should be package-level variables (`var ErrNotFound = ...`)
- [ ] Detect error handling in deferred functions that shadow outer errors
- [ ] Identify panic recovery (`recover()`) in wrong places or missing entirely
- [ ] Check for proper error type hierarchy and categorization

### 3.2 Panic & Recovery
- [ ] Find `panic()` calls in library code (should return errors instead)
- [ ] Identify missing `recover()` in goroutines (unrecovered panic kills process)
- [ ] Detect `log.Fatal()` / `os.Exit()` in library code (only acceptable in `main`)
- [ ] Find index out of range possibilities without bounds checking
- [ ] Identify `panic` in `init()` functions without clear documentation
- [ ] Check for proper panic recovery in HTTP handlers / middleware
- [ ] Find `must` pattern functions without clear naming convention
- [ ] Detect panics in hot paths where error return is feasible

### 3.3 Error Wrapping & Context
- [ ] Find error messages that don't include contextual information (which operation, which input)
- [ ] Identify error wrapping that creates excessively deep chains
- [ ] Detect inconsistent error wrapping style across the codebase
- [ ] Check for `fmt.Errorf("...: %w", err)` with proper verb usage
- [ ] Find places where structured errors (error types) should replace string errors
- [ ] Identify missing stack trace information in critical error paths
- [ ] Check for error messages that leak sensitive information (passwords, tokens, PII)

---

## 4. CONCURRENCY & GOROUTINES

### 4.1 Goroutine Management
- [ ] Find goroutine leaks (goroutines started but never terminated)
- [ ] Identify goroutines without proper shutdown mechanism (context cancellation)
- [ ] Detect goroutines launched in loops without controlling concurrency
- [ ] Find fire-and-forget goroutines without error reporting
- [ ] Identify goroutines that outlive the function that created them
- [ ] Check for `go func()` capturing loop variables (Go <1.22 issue)
- [ ] Find goroutine pools that grow unbounded
- [ ] Detect goroutines without `recover()` for panic safety
- [ ] Identify missing `sync.WaitGroup` for goroutine completion tracking
- [ ] Check for proper use of `errgroup.Group` for error-propagating goroutine groups

### 4.2 Channel Issues
- [ ] Find unbuffered channels that could cause deadlocks
- [ ] Identify channels that are never closed (potential goroutine leaks)
- [ ] Detect double-close on channels (runtime panic)
- [ ] Find send on closed channel (runtime panic)
- [ ] Identify missing `select` with `default` for non-blocking operations
- [ ] Check for missing `context.Done()` case in select statements
- [ ] Find channel direction missing in function signatures (`chan T` vs `<-chan T` vs `chan<- T`)
- [ ] Detect channels used as mutexes where `sync.Mutex` is clearer
- [ ] Identify channel buffer sizes that are arbitrary without justification
- [ ] Check for fan-out/fan-in patterns without proper coordination

### 4.3 Race Conditions & Synchronization
- [ ] Find shared mutable state accessed without synchronization
- [ ] Identify `sync.Map` used where regular `map` + `sync.RWMutex` is better (or vice versa)
- [ ] Detect lock ordering issues that could cause deadlocks
- [ ] Find `sync.Mutex` that should be `sync.RWMutex` for read-heavy workloads
- [ ] Identify atomic operations that should be used instead of mutex for simple counters
- [ ] Check for `sync.Once` used correctly (especially with errors)
- [ ] Find data races in struct field access from multiple goroutines
- [ ] Detect time-of-check to time-of-use (TOCTOU) vulnerabilities
- [ ] Identify lock held during I/O operations (blocking under lock)
- [ ] Check for proper use of `sync.Pool` (object resetting, Put after Get)
- [ ] Find missing `go vet -race` / `-race` flag testing evidence
- [ ] Detect `sync.Cond` misuse (missing broadcast/signal)

### 4.4 Context Usage
- [ ] Find functions accepting `context.Context` not as first parameter
- [ ] Identify `context.Background()` used where parent context should be propagated
- [ ] Detect `context.TODO()` left in production code
- [ ] Find context cancellation not being checked in long-running operations
- [ ] Identify context values used for passing request-scoped data inappropriately
- [ ] Check for context leaks (missing cancel function calls)
- [ ] Find `context.WithTimeout`/`WithDeadline` without `defer cancel()`
- [ ] Detect context stored in structs (should be passed as parameter)

---

## 5. RESOURCE MANAGEMENT

### 5.1 Defer & Cleanup
- [ ] Find `defer` inside loops (defers don't run until function returns)
- [ ] Identify `defer` with captured loop variables
- [ ] Detect missing `defer` for resource cleanup (file handles, connections, locks)
- [ ] Find `defer` order issues (LIFO behavior not accounted for)
- [ ] Identify `defer` on methods that could fail silently (`defer f.Close()` — error ignored)
- [ ] Check for `defer` with named return values interaction (late binding)
- [ ] Find resources opened but never closed (file descriptors, HTTP response bodies)
- [ ] Detect `http.Response.Body` not being closed after read
- [ ] Identify database rows/statements not being closed

### 5.2 Memory Management
- [ ] Find large allocations in hot paths
- [ ] Identify slice capacity hints missing (`make([]T, 0, expectedSize)`)
- [ ] Detect string builder not used for string concatenation in loops
- [ ] Find `append()` growing slices without capacity pre-allocation
- [ ] Identify byte slice to string conversion in hot paths (allocation)
- [ ] Check for proper use of `sync.Pool` for frequently allocated objects
- [ ] Find large structs passed by value instead of pointer
- [ ] Detect slice reslicing that prevents garbage collection of underlying array
- [ ] Identify `map` that grows but never shrinks (memory leak pattern)
- [ ] Check for proper buffer reuse in I/O operations (`bufio`, `bytes.Buffer`)

### 5.3 File & I/O Resources
- [ ] Find `os.Open` / `os.Create` without `defer f.Close()`
- [ ] Identify `io.ReadAll` on potentially large inputs (OOM risk)
- [ ] Detect missing `bufio.Scanner` / `bufio.Reader` for large file reading
- [ ] Find temporary files not cleaned up
- [ ] Identify `os.TempDir()` usage without proper cleanup
- [ ] Check for file permissions too permissive (0777, 0666)
- [ ] Find missing `fsync` for critical writes
- [ ] Detect race conditions on file operations

---

## 6. SECURITY VULNERABILITIES

### 6.1 Injection Attacks
- [ ] Find SQL queries built with `fmt.Sprintf` instead of parameterized queries
- [ ] Identify command injection via `exec.Command` with user input
- [ ] Detect path traversal vulnerabilities (`filepath.Join` with user input without `filepath.Clean`)
- [ ] Find template injection in `html/template` or `text/template`
- [ ] Identify log injection possibilities (user input in log messages without sanitization)
- [ ] Check for LDAP injection vulnerabilities
- [ ] Find header injection in HTTP responses
- [ ] Detect SSRF vulnerabilities (user-controlled URLs in HTTP requests)
- [ ] Identify deserialization attacks via `encoding/gob`, `encoding/json` with `interface{}`
- [ ] Check for regex injection (ReDoS) with user-provided patterns

### 6.2 Authentication & Authorization
- [ ] Find hardcoded credentials, API keys, or secrets in source code
- [ ] Identify missing authentication middleware on protected endpoints
- [ ] Detect authorization bypass possibilities (IDOR vulnerabilities)
- [ ] Find JWT implementation flaws (algorithm confusion, missing validation)
- [ ] Identify timing attacks in comparison operations (use `crypto/subtle.ConstantTimeCompare`)
- [ ] Check for proper password hashing (`bcrypt`, `argon2`, NOT `md5`/`sha256`)
- [ ] Find session tokens with insufficient entropy
- [ ] Detect privilege escalation via role/permission bypass
- [ ] Identify missing CSRF protection on state-changing endpoints
- [ ] Check for proper OAuth2 implementation (state parameter, PKCE)

### 6.3 Cryptographic Issues
- [ ] Find use of `math/rand` instead of `crypto/rand` for security purposes
- [ ] Identify weak hash algorithms (`md5`, `sha1`) for security-sensitive operations
- [ ] Detect hardcoded encryption keys or IVs
- [ ] Find ECB mode usage (should use GCM, CTR, or CBC with proper IV)
- [ ] Identify missing TLS configuration or insecure `InsecureSkipVerify: true`
- [ ] Check for proper certificate validation
- [ ] Find deprecated crypto packages or algorithms
- [ ] Detect nonce reuse in encryption
- [ ] Identify HMAC comparison without constant-time comparison

### 6.4 Input Validation & Sanitization
- [ ] Find missing input length/size limits
- [ ] Identify `io.ReadAll` without `io.LimitReader` (denial of service)
- [ ] Detect missing Content-Type validation on uploads
- [ ] Find integer overflow/underflow in size calculations
- [ ] Identify missing URL validation before HTTP requests
- [ ] Check for proper handling of multipart form data limits
- [ ] Find missing rate limiting on public endpoints
- [ ] Detect unvalidated redirects (open redirect vulnerability)
- [ ] Identify user input used in file paths without sanitization
- [ ] Check for proper CORS configuration

### 6.5 Data Security
- [ ] Find sensitive data in logs (passwords, tokens, PII)
- [ ] Identify PII stored without encryption at rest
- [ ] Detect sensitive data in URL query parameters
- [ ] Find sensitive data in error messages returned to clients
- [ ] Identify missing `Secure`, `HttpOnly`, `SameSite` cookie flags
- [ ] Check for sensitive data in environment variables logged at startup
- [ ] Find API responses that leak internal implementation details
- [ ] Detect missing response headers (CSP, HSTS, X-Frame-Options)

---

## 7. PERFORMANCE ANALYSIS

### 7.1 Algorithmic Complexity
- [ ] Find O(n²) or worse algorithms that could be optimized
- [ ] Identify nested loops that could be flattened
- [ ] Detect repeated slice/map iterations that could be combined
- [ ] Find linear searches that should use `map` for O(1) lookup
- [ ] Identify sorting operations that could be avoided with a heap/priority queue
- [ ] Check for unnecessary slice copying (`append`, spread)
- [ ] Find recursive functions without memoization
- [ ] Detect expensive operations inside hot loops

### 7.2 Go-Specific Performance
- [ ] Find excessive allocations detectable by escape analysis (`go build -gcflags="-m"`)
- [ ] Identify interface boxing in hot paths (causes allocation)
- [ ] Detect excessive use of `fmt.Sprintf` where `strconv` functions are faster
- [ ] Find `reflect` usage in hot paths
- [ ] Identify `defer` in tight loops (overhead per iteration)
- [ ] Check for string → []byte → string conversions that could be avoided
- [ ] Find JSON marshaling/unmarshaling in hot paths (consider code-gen alternatives)
- [ ] Detect map iteration where order matters (Go maps are unordered)
- [ ] Identify `time.Now()` calls in tight loops (syscall overhead)
- [ ] Check for proper use of `sync.Pool` in allocation-heavy code
- [ ] Find `regexp.Compile` called repeatedly (should be package-level `var`)
- [ ] Detect `append` without pre-allocated capacity in known-size operations

### 7.3 I/O Performance
- [ ] Find synchronous I/O in goroutine-heavy code that could block
- [ ] Identify missing connection pooling for database/HTTP clients
- [ ] Detect missing buffered I/O (`bufio.Reader`/`bufio.Writer`)
- [ ] Find `http.Client` without timeout configuration
- [ ] Identify missing `http.Client` reuse (creating new client per request)
- [ ] Check for `http.DefaultClient` usage (no timeout by default)
- [ ] Find database queries without `LIMIT` clause
- [ ] Detect N+1 query problems in data fetching
- [ ] Identify missing prepared statements for repeated queries
- [ ] Check for missing response body draining before close (`io.Copy(io.Discard, resp.Body)`)

### 7.4 Memory Performance
- [ ] Find large struct copying on each function call (pass by pointer)
- [ ] Identify slice backing array leaks (sub-slicing prevents GC)
- [ ] Detect `map` growing indefinitely without cleanup/eviction
- [ ] Find string concatenation in loops (use `strings.Builder`)
- [ ] Identify closure capturing large objects unnecessarily
- [ ] Check for proper `bytes.Buffer` reuse
- [ ] Find `ioutil.ReadAll` (deprecated and unbounded reads)
- [ ] Detect pprof/benchmark evidence missing for performance claims

---

## 8. CODE QUALITY ISSUES

### 8.1 Dead Code Detection
- [ ] Find unused exported functions/methods/types
- [ ] Identify unreachable code after `return`/`panic`/`os.Exit`
- [ ] Detect unused function parameters
- [ ] Find unused struct fields
- [ ] Identify unused imports (should be caught by compiler, but check generated code)
- [ ] Check for commented-out code blocks
- [ ] Find unused type definitions
- [ ] Detect unused constants/variables
- [ ] Identify build-tagged code that's never compiled
- [ ] Find orphaned test helper functions

### 8.2 Code Duplication
- [ ] Find duplicate function implementations across packages
- [ ] Identify copy-pasted code blocks with minor variations
- [ ] Detect similar logic that could be abstracted into shared functions
- [ ] Find duplicate struct definitions
- [ ] Identify repeated error handling boilerplate that could be middleware
- [ ] Check for duplicate validation logic
- [ ] Find similar HTTP handler patterns that could be generalized
- [ ] Detect duplicate constants across packages

### 8.3 Code Smells
- [ ] Find functions longer than 50 lines
- [ ] Identify files larger than 500 lines (split into multiple files)
- [ ] Detect deeply nested conditionals (>3 levels) — use early returns
- [ ] Find functions with too many parameters (>5) — use options pattern or config struct
- [ ] Identify God packages with too many responsibilities
- [ ] Check for `init()` functions with side effects (hard to test, order-dependent)
- [ ] Find `switch` statements that should be polymorphism (interface dispatch)
- [ ] Detect boolean parameters (use options or separate functions)
- [ ] Identify data clumps (groups of parameters that appear together)
- [ ] Find speculative generality (unused abstractions/interfaces)

### 8.4 Go Idioms & Style
- [ ] Find non-idiomatic error handling (not following `if err != nil` pattern)
- [ ] Identify getters with `Get` prefix (Go convention: `Name()` not `GetName()`)
- [ ] Detect unexported types returned from exported functions
- [ ] Find package names that stutter (`http.HTTPClient` → `http.Client`)
- [ ] Identify `else` blocks after `if-return` (should be flat)
- [ ] Check for proper use of `iota` for enumerations
- [ ] Find exported functions without documentation comments
- [ ] Detect `var` declarations where `:=` is cleaner (and vice versa)
- [ ] Identify missing package-level documentation (`// Package foo ...`)
- [ ] Check for proper receiver naming (short, consistent: `s` for `Server`, not `this`/`self`)
- [ ] Find single-method interface names not ending in `-er` (`Reader`, `Writer`, `Closer`)
- [ ] Detect naked returns in non-trivial functions

---

## 9. ARCHITECTURE & DESIGN

### 9.1 Package Structure
- [ ] Find circular dependencies between packages (`go vet ./...` won't compile but check indirect)
- [ ] Identify `internal/` packages missing where they should exist
- [ ] Detect "everything in one package" anti-pattern
- [ ] Find improper package layering (business logic importing HTTP handlers)
- [ ] Identify missing clean architecture boundaries (domain, service, repository layers)
- [ ] Check for proper `cmd/` structure for multiple binaries
- [ ] Find shared mutable global state across packages
- [ ] Detect `pkg/` directory misuse
- [ ] Identify missing dependency injection (constructors accepting interfaces)
- [ ] Check for proper separation between API definition and implementation

### 9.2 SOLID Principles
- [ ] **Single Responsibility**: Find packages/files doing too much
- [ ] **Open/Closed**: Find code requiring modification for extension (missing interfaces/plugins)
- [ ] **Liskov Substitution**: Find interface implementations that violate contracts
- [ ] **Interface Segregation**: Find fat interfaces that should be split
- [ ] **Dependency Inversion**: Find concrete type dependencies where interfaces should be used

### 9.3 Design Patterns
- [ ] Find missing `Functional Options` pattern for configurable types
- [ ] Identify `New*` constructor functions that should accept `Option` funcs
- [ ] Detect missing middleware pattern for cross-cutting concerns
- [ ] Find observer/pubsub implementations that could leak goroutines
- [ ] Identify missing `Repository` pattern for data access
- [ ] Check for proper `Builder` pattern for complex object construction
- [ ] Find missing `Strategy` pattern opportunities (behavior variation via interface)
- [ ] Detect global state that should use dependency injection

### 9.4 API Design
- [ ] Find HTTP handlers that do business logic directly (should delegate to service layer)
- [ ] Identify missing request/response validation middleware
- [ ] Detect inconsistent REST API conventions across endpoints
- [ ] Find gRPC service definitions without proper error codes
- [ ] Identify missing API versioning strategy
- [ ] Check for proper HTTP status code usage
- [ ] Find missing health check / readiness endpoints
- [ ] Detect overly chatty APIs (N+1 endpoints that should be batched)

---

## 10. DEPENDENCY ANALYSIS

### 10.1 Module & Version Analysis
- [ ] Run `go list -m -u all` — identify all outdated dependencies
- [ ] Check `go.sum` consistency (`go mod verify`)
- [ ] Find replace directives left in `go.mod`
- [ ] Identify dependencies with known CVEs (`govulncheck ./...`)
- [ ] Check for unused dependencies (`go mod tidy` changes)
- [ ] Find vendored dependencies that are outdated
- [ ] Identify indirect dependencies that should be direct
- [ ] Check for Go version in `go.mod` matching CI/deployment target
- [ ] Find `//go:build ignore` files with dependency imports

### 10.2 Dependency Health
- [ ] Check last commit date for each dependency
- [ ] Identify archived/unmaintained dependencies
- [ ] Find dependencies with open critical issues
- [ ] Check for dependencies using `unsafe` package extensively
- [ ] Identify heavy dependencies that could be replaced with stdlib
- [ ] Find dependencies with restrictive licenses (GPL in MIT project)
- [ ] Check for dependencies with CGO requirements (portability concern)
- [ ] Identify dependencies pulling in massive transitive trees
- [ ] Find forked dependencies without upstream tracking

### 10.3 CGO Considerations
- [ ] Check if CGO is required and if `CGO_ENABLED=0` build is possible
- [ ] Find CGO code without proper memory management
- [ ] Identify CGO calls in hot paths (overhead of Go→C boundary crossing)
- [ ] Check for CGO dependencies that break cross-compilation
- [ ] Find CGO code that doesn't handle C errors properly
- [ ] Detect potential memory leaks across CGO boundary

---

## 11. TESTING GAPS

### 11.1 Coverage Analysis
- [ ] Run `go test -coverprofile` — identify untested packages and functions
- [ ] Find untested error paths (especially error returns)
- [ ] Detect untested edge cases in conditionals
- [ ] Check for missing boundary value tests
- [ ] Identify untested concurrent scenarios
- [ ] Find untested input validation paths
- [ ] Check for missing integration tests (database, HTTP, gRPC)
- [ ] Identify critical paths without benchmark tests (`*testing.B`)

### 11.2 Test Quality
- [ ] Find tests that don't use `t.Helper()` for test helper functions
- [ ] Identify table-driven tests that should exist but don't
- [ ] Detect tests with excessive mocking hiding real bugs
- [ ] Find tests that test implementation instead of behavior
- [ ] Identify tests with shared mutable state (run order dependent)
- [ ] Check for `t.Parallel()` usage where safe
- [ ] Find flaky tests (timing-dependent, file-system dependent)
- [ ] Detect missing subtests (`t.Run("name", ...)`)
- [ ] Identify missing `testdata/` files for golden tests
- [ ] Check for `httptest.NewServer` cleanup (missing `defer server.Close()`)

### 11.3 Test Infrastructure
- [ ] Find missing `TestMain` for setup/teardown
- [ ] Identify missing build tags for integration tests (`//go:build integration`)
- [ ] Detect missing race condition tests (`go test -race`)
- [ ] Check for missing fuzz tests (`Fuzz*` functions — Go 1.18+)
- [ ] Find missing example tests (`Example*` functions for godoc)
- [ ] Identify missing benchmark comparison baselines
- [ ] Check for proper test fixture management
- [ ] Find tests relying on external services without mocks/stubs

---

## 12. CONFIGURATION & BUILD

### 12.1 Go Module Configuration
- [ ] Check Go version in `go.mod` is appropriate
- [ ] Verify `go.sum` is committed and consistent
- [ ] Check for proper module path naming
- [ ] Find replace directives that shouldn't be in published modules
- [ ] Identify retract directives needed for broken versions
- [ ] Check for proper module boundaries (when to split)
- [ ] Verify `//go:generate` directives are documented and reproducible

### 12.2 Build Configuration
- [ ] Check for proper `ldflags` for version embedding
- [ ] Verify `CGO_ENABLED` setting is intentional
- [ ] Find build tags used correctly (`//go:build`)
- [ ] Check for proper cross-compilation setup
- [ ] Identify missing `go vet` / `staticcheck` / `golangci-lint` in CI
- [ ] Verify Docker multi-stage build for minimal image size
- [ ] Check for proper `.goreleaser.yml` configuration if applicable
- [ ] Find hardcoded `GOOS`/`GOARCH` where build tags should be used

### 12.3 Environment & Configuration
- [ ] Find hardcoded environment-specific values (URLs, ports, paths)
- [ ] Identify missing environment variable validation at startup
- [ ] Detect improper fallback values for missing configuration
- [ ] Check for proper config struct with validation tags
- [ ] Find sensitive values not using secrets management
- [ ] Identify missing feature flags / toggles for gradual rollout
- [ ] Check for proper signal handling (`SIGTERM`, `SIGINT`) for graceful shutdown
- [ ] Find missing health check endpoints (`/healthz`, `/readyz`)

---

## 13. HTTP & NETWORK SPECIFIC

### 13.1 HTTP Server Issues
- [ ] Find `http.ListenAndServe` without timeouts (use custom `http.Server`)
- [ ] Identify missing `ReadTimeout`, `WriteTimeout`, `IdleTimeout` on server
- [ ] Detect missing `http.MaxBytesReader` on request bodies
- [ ] Find response headers not set (Content-Type, Cache-Control, Security headers)
- [ ] Identify missing graceful shutdown with `server.Shutdown(ctx)`
- [ ] Check for proper middleware chaining order
- [ ] Find missing request ID / correlation ID propagation
- [ ] Detect missing access logging middleware
- [ ] Identify missing panic recovery middleware
- [ ] Check for proper handler error response consistency

### 13.2 HTTP Client Issues
- [ ] Find `http.DefaultClient` usage (no timeout)
- [ ] Identify `http.Response.Body` not closed after use
- [ ] Detect missing retry logic with exponential backoff
- [ ] Find missing `context.Context` propagation in HTTP calls
- [ ] Identify connection pool exhaustion risks (missing `MaxIdleConns` tuning)
- [ ] Check for proper TLS configuration on client
- [ ] Find missing `io.LimitReader` on response body reads
- [ ] Detect DNS caching issues in long-running processes

### 13.3 Database Issues
- [ ] Find `database/sql` connections not using connection pool properly
- [ ] Identify missing `SetMaxOpenConns`, `SetMaxIdleConns`, `SetConnMaxLifetime`
- [ ] Detect SQL injection via string concatenation
- [ ] Find missing transaction rollback on error (`defer tx.Rollback()`)
- [ ] Identify `rows.Close()` missing after `db.Query()`
- [ ] Check for `rows.Err()` check after iteration
- [ ] Find missing prepared statement caching
- [ ] Detect context not passed to database operations
- [ ] Identify missing database migration versioning

---

## 14. DOCUMENTATION & MAINTAINABILITY

### 14.1 Code Documentation
- [ ] Find exported functions/types/constants without godoc comments
- [ ] Identify functions with complex logic but no explanation
- [ ] Detect missing package-level documentation (`// Package foo ...`)
- [ ] Check for outdated comments that no longer match code
- [ ] Find TODO/FIXME/HACK/XXX comments that need addressing
- [ ] Identify magic numbers without named constants
- [ ] Check for missing examples in godoc (`Example*` functions)
- [ ] Find missing error documentation (what errors can be returned)

### 14.2 Project Documentation
- [ ] Find missing README with usage, installation, API docs
- [ ] Identify missing CHANGELOG
- [ ] Detect missing CONTRIBUTING guide
- [ ] Check for missing architecture decision records (ADRs)
- [ ] Find missing API documentation (OpenAPI/Swagger, protobuf docs)
- [ ] Identify missing deployment/operations documentation
- [ ] Check for missing LICENSE file

---

## 15. EDGE CASES CHECKLIST

### 15.1 Input Edge Cases
- [ ] Empty strings, slices, maps
- [ ] `math.MaxInt64`, `math.MinInt64`, overflow boundaries
- [ ] Negative numbers where positive expected
- [ ] Zero values for all types
- [ ] `math.NaN()` and `math.Inf()` in float operations
- [ ] Unicode characters and emoji in string processing
- [ ] Very large inputs (>1GB files, millions of records)
- [ ] Deeply nested JSON structures
- [ ] Malformed input data (truncated JSON, broken UTF-8)
- [ ] Concurrent access from multiple goroutines

### 15.2 Timing Edge Cases
- [ ] Leap years and daylight saving time transitions
- [ ] Timezone handling (`time.UTC` vs `time.Local` inconsistencies)
- [ ] `time.Ticker` / `time.Timer` not stopped (goroutine leak)
- [ ] Monotonic clock vs wall clock (`time.Now()` uses monotonic for duration)
- [ ] Very old timestamps (before Unix epoch)
- [ ] Nanosecond precision issues in comparisons
- [ ] `time.After()` in select statements (creates new channel each iteration — leak)

### 15.3 Platform Edge Cases
- [ ] File path handling across OS (`filepath.Join` vs `path.Join`)
- [ ] Line ending differences (`\n` vs `\r\n`)
- [ ] File system case sensitivity differences
- [ ] Maximum path length constraints
- [ ] Endianness assumptions in binary protocols
- [ ] Signal handling differences across OS

---

## OUTPUT FORMAT

For each issue found, provide:

### [SEVERITY: CRITICAL/HIGH/MEDIUM/LOW] Issue Title

**Category**: [Type Safety/Security/Concurrency/Performance/etc.]
**File**: path/to/file.go
**Line**: 123-145
**Impact**: Description of what could go wrong

**Current Code**:
```go
// problematic code
```

**Problem**: Detailed explanation of why this is an issue

**Recommendation**:
```go
// fixed code
```

**References**: Links to documentation, Go blog posts, CVEs, best practices

---

## PRIORITY MATRIX

1. **CRITICAL** (Fix Immediately):
   - Security vulnerabilities (injection, auth bypass)
   - Data loss / corruption risks
   - Race conditions causing panics in production
   - Goroutine leaks causing OOM

2. **HIGH** (Fix This Sprint):
   - Nil pointer dereferences
   - Ignored errors in critical paths
   - Missing context cancellation
   - Resource leaks (connections, file handles)

3. **MEDIUM** (Fix Soon):
   - Code quality / idiom violations
   - Test coverage gaps
   - Performance issues in non-hot paths
   - Documentation gaps

4. **LOW** (Tech Debt):
   - Style inconsistencies
   - Minor optimizations
   - Nice-to-have abstractions
   - Naming improvements

---

## STATIC ANALYSIS TOOLS TO RUN

Before manual review, run these tools and include findings:

```bash
# Compiler checks
go build ./...
go vet ./...

# Race detector
go test -race ./...

# Vulnerability check
govulncheck ./...

# Linter suite (comprehensive)
golangci-lint run --enable-all ./...

# Dead code detection
deadcode ./...

# Unused exports
unused ./...

# Security scanner
gosec ./...

# Complexity analysis
gocyclo -over 15 .

# Escape analysis
go build -gcflags="-m -m" ./... 2>&1 | grep "escapes to heap"

# Test coverage
go test -coverprofile=coverage.out ./...
go tool cover -func=coverage.out
```

---

## FINAL SUMMARY

After completing the review, provide:

1. **Executive Summary**: 2-3 paragraphs overview
2. **Risk Assessment**: Overall risk level with justification
3. **Top 10 Critical Issues**: Prioritized list
4. **Recommended Action Plan**: Phased approach to fixes
5. **Estimated Effort**: Time estimates for remediation
6. **Metrics**:
   - Total issues found by severity
   - Code health score (1-10)
   - Security score (1-10)
   - Concurrency safety score (1-10)
   - Maintainability score (1-10)
   - Test coverage percentage