Golang Concurrency

Priority: P0 (CRITICAL)

Principles

• Share Memory by Communicating: Use channels instead of shared memory.
• Context is King: Always pass ctx to manage cancellation/timeouts.
• Prevent Leaks: Never start a 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 does I/O or long work must accept context.Context.
3. Define exit paths — Every goroutine must have a 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

• ❌ Goroutine leaks — every goroutine needs a known exit path
• ❌ Global state mutation across goroutines — use channels or sync primitives
• ❌ Bare goroutines without lifecycle management — use errgroup or WaitGroup

References

• Concurrency Patterns
• Context Usage