golang-concurrency

name	golang-concurrency
description	Standards for safe concurrent programming using Goroutines, Channels, and Context. Use when implementing concurrency with Goroutines, Channels, or Context in Go. (triggers: goroutine, go keyword, channel, mutex, waitgroup, context, errgroup, race condition)

Golang Concurrency Standards

Priority: P0 (CRITICAL)

Principles

• Share Memory by Communicating: Don't communicate by sharing memory. Use channels.
• Context is King: Always pass ctx to efficient manage cancellation/timeouts.
• Prevent Leaks: Never start a goroutine without knowing how it will stop.
• Race Detection: Always run tests with go test -race.

Primitives

• Goroutines: Lightweight threads. go func() { ... }()
• Channels: For data passing + synchronization.
• WaitGroup: Wait for a group of goroutines to finish.
• ErrGroup: WaitGroup + Error propagation (Preferred).
• Mutex: Protect shared state (simpler than channels for just state).

Guidelines

• Buffered vs Unbuffered: Use unbuffered channels for strict synchronization. Use buffered only if you specifically need async decoupling/burst handling.
• Closed Channels: Panic if writing to closed. Reading from closed returns zero-value immediately.
• Select: Use select to handle multiple channels or timeouts.

References

• Concurrency Patterns
• Context Usage

Anti-Patterns

• No goroutine leaks: Every goroutine needs a known exit path.
• No global state mutation across goroutines: Use channels or sync primitives.
• No bare goroutines without lifecycle: Use errgroup or WaitGroup.