Golang Pitfalls: Concurrency Practice

Source material: mistakes #61-74 from 100 Go Mistakes and How to Avoid Them (teivah/100-go-mistakes).

Apply these rules when writing practical Go concurrency code.

61. Propagating an inappropriate context (#61)

• An HTTP request context is canceled when: the client's connection closes, the request is canceled (HTTP/2), or the response is written.
• If you spawn an async goroutine (e.g., Kafka publish) using the request context, the context may be canceled right after the response is written, silently dropping the work.
• Propagate with care; from Go 1.21 you can use context.WithoutCancel(parent) for work that must outlive the request.

62. Starting a goroutine without knowing when to stop it (#62)

• Every goroutine is a resource; always have a plan to stop it — otherwise goroutine/resource leaks.
• Signaling alone (a canceled context) isn't enough; the parent may exit before the goroutine cleans up.
• If a goroutine's lifetime is bound to the app's, wait for it to finish before returning: expose a close() (use defer w.close()) or wait for completion.

63. Goroutines and loop variables (#63)