From golang-skills
Guides Go concurrency: goroutine lifetimes with WaitGroups, channels for communication, mutexes for shared state, preventing leaks and data races.
npx claudepluginhub cxuu/golang-skills --plugin golang-skillsThis skill uses the workspace's default tool permissions.
> **Normative**: When you spawn goroutines, make it clear when or whether they
Implements, reviews, and audits Go concurrency patterns with goroutines, channels, select, locks, sync primitives, errgroup, worker pools, and pipelines. Detects leaks, races, and ownership issues.
Guides writing, reviewing, and auditing concurrent Go code using goroutines, channels, select, locks, sync primitives, errgroup, singleflight, and worker pools. Detects leaks, races, and ownership issues.
Reviews and implements safe Go concurrency patterns: goroutines, channels, sync primitives, context propagation, lifecycle management. Use for thread safety checks, race debugging, producer/consumer pipelines.
Share bugs, ideas, or general feedback.
Normative: When you spawn goroutines, make it clear when or whether they exit.
Goroutines can leak by blocking on channel sends/receives. The GC will not terminate a blocked goroutine even if no other goroutine holds a reference to the channel. Even non-leaking in-flight goroutines cause panics (send on closed channel), data races, memory issues, and resource leaks.
init() — expose lifecycle methods (Close, Stop,
Shutdown) instead// Good: Clear lifetime with WaitGroup
var wg sync.WaitGroup
for item := range queue {
wg.Add(1)
go func() { defer wg.Done(); process(ctx, item) }()
}
wg.Wait()
// Bad: No way to stop or wait
go func() { for { flush(); time.Sleep(delay) } }()
Test for leaks with go.uber.org/goleak.
Principle: Never start a goroutine without knowing how it will stop.
Read references/GOROUTINE-PATTERNS.md when implementing stop/done channel patterns, goroutine waiting strategies, or lifecycle-managed workers.
"Do not communicate by sharing memory; instead, share memory by communicating."
This is Go's foundational concurrency design principle. Use channels for ownership transfer and orchestration — when one goroutine produces a value and another consumes it. Use mutexes when multiple goroutines access shared state and channels would add unnecessary complexity.
Default to channels. Fall back to sync.Mutex / sync.RWMutex when the
problem is naturally about protecting a shared data structure (e.g., a cache or
counter) rather than passing data between goroutines.
Normative: Prefer synchronous functions over asynchronous ones.
| Benefit | Why |
|---|---|
| Localized goroutines | Lifetimes easier to reason about |
| Avoids leaks and races | Easier to prevent resource leaks and data races |
| Easier to test | Check input/output without polling |
| Caller flexibility | Caller adds concurrency when needed |
Advisory: It is quite difficult (sometimes impossible) to remove unnecessary concurrency at the caller side. Let the caller add concurrency when needed.
Read references/GOROUTINE-PATTERNS.md when writing synchronous-first APIs that callers may wrap in goroutines.
The zero-value of sync.Mutex and sync.RWMutex is valid — almost never need
a pointer to a mutex.
// Good: Zero-value is valid // Bad: Unnecessary pointer
var mu sync.Mutex mu := new(sync.Mutex)
Don't embed mutexes — use a named mu field to keep Lock/Unlock as
implementation details, not exported API.
Read references/SYNC-PRIMITIVES.md when implementing mutex-protected structs or deciding how to structure mutex fields.
Normative: Specify channel direction where possible.
Direction prevents errors (compiler catches closing a receive-only channel), conveys ownership, and is self-documenting.
func produce(out chan<- int) { /* send-only */ }
func consume(in <-chan int) { /* receive-only */ }
func transform(in <-chan int, out chan<- int) { /* both */ }
Channels should have size zero (unbuffered) or one. Any other size requires justification for:
c := make(chan int) // unbuffered — Good
c := make(chan int, 1) // size one — Good
c := make(chan int, 64) // arbitrary — needs justification
Read references/SYNC-PRIMITIVES.md when reviewing detailed channel direction examples with error-prone patterns.
Use atomic.Bool, atomic.Int64, etc. (stdlib sync/atomic since Go 1.19, or
go.uber.org/atomic) for type-safe
atomic operations. Raw int32/int64 fields make it easy to forget atomic
access on some code paths.
// Good: Type-safe // Bad: Easy to forget
var running atomic.Bool var running int32 // atomic
running.Store(true) atomic.StoreInt32(&running, 1)
running.Load() running == 1 // race!
Read references/SYNC-PRIMITIVES.md when choosing between sync/atomic and go.uber.org/atomic, or implementing atomic state flags in structs.
Advisory: Document thread-safety when it's not obvious from the operation type.
Go users assume read-only operations are safe for concurrent use, and mutating operations are not. Document concurrency when:
Lookup that mutates LRU stateFor context.Context guidance (parameter placement, struct storage, custom types, derivation patterns), see the dedicated go-context skill.
Use a buffered channel as a free list to reuse allocated buffers. This "leaky
buffer" pattern uses select with default for non-blocking operations.
Read references/BUFFER-POOLING.md when implementing a worker pool with reusable buffers or choosing between channel-based pools and
sync.Pool.
Read references/ADVANCED-PATTERNS.md when implementing request-response multiplexing with channels of channels, or CPU-bound parallel computation across cores.