golang-concurrency

name	golang-concurrency
description	Write safe concurrent Go code with goroutines, channels, and context. Use when implementing concurrency with goroutines, channels, or context in Go.
metadata	{"triggers":{"keywords":["goroutine","go keyword","channel","mutex","waitgroup","context","errgroup","race condition"]}}

Golang Concurrency

Priority: P0 (CRITICAL)

Principles

• Share Memory by Communicating: Use channels instead of shared memory.
• Context King: Always pass ctx to manage cancellation/timeouts.
• Prevent Leaks: Never start goroutine without knowing how it will stop.
• Race Detection: Always run tests with go test -race.

Implementation Workflow

1. Choose primitive — Channels for data passing, sync.Mutex for simple state protection, errgroup for parallel tasks with error handling.
2. Pass context — Every goroutine that I/O or long work must accept context.Context.
3. Define exit paths — Every goroutine must clear shutdown mechanism (context cancellation, channel close, or WaitGroup).
4. Use select for multiplexing — Handle multiple channels or timeouts with select.
5. Test with race detector — Run go test -race in CI.

See ErrGroup and concurrency patterns and context timeout examples

Anti-Patterns

• No goroutine leaks: ensure every goroutine known exit path.
• No shared global state: use channels or sync primitives across goroutines.
• No bare goroutines: use errgroup or WaitGroup for lifecycle management.

References

• Concurrency Patterns
• Context Usage