go-concurrency-review

# Go Concurrency Review ## Purpose Identify concurrency defects and goroutine lifecycle issues in Go code. Scope: race conditions, deadlocks, goroutine leaks, mutex misuse, context propagation, and lifecycle management. This skill does NOT cover: security vulnerabilities, performance optimization, code style, test quality, error handling patterns, or business logic — those belong to sibling vertical skills. ## When To Use - Code contains `go func`, goroutine creation - Code uses channels, `sync` primitives (Mutex, RWMutex, WaitGroup) - Code uses `errgroup`, `singleflight` - Code involves context propagation and cancellation - Code contains graceful shutdown logic ## When NOT To Use - Security vulnerabilities → `go-security-review` - Performance optimization (lock contention as perf issue) → `go-performance-review` - Code style/lint → `go-quality-review` - Error handling correctness → `go-error-review` - Business logic → `go-logic-review` ## Mandatory Gates ### 1) Execution Integrity Gate Never claim `go test -race` ran unless it actually produced output. If not run: state reason + exact command. ### 2) Go Version Gate Read `go.mod` for `go` directive. Key version gates: - `errgroup.SetLimit` (Go 1.20+) - `sync.OnceValue` / `sync.OnceFunc` (Go 1.21+) - Loop variable fix (Go 1.22+) — do NOT flag loop variable capture in Go ≥ 1.22 ### 3) Anti-Example Suppression Gate MUST quote specific code evidence satisfying precondition. Category match alone insufficient. Embedded ...