Channel closing

Canonical guidance

• the sending side closes when it knows no more values will arrive
• receivers do not close channels they do not own
• close channels for completion signals, not acknowledgments

Use when

• producer completion
• pipeline shutdown
• fan-out workers consuming a finite stream

Avoid

• multiple senders racing to close the same channel
• closing from the receive side
• treating close as a generic broadcast for unrelated state changes

Preferred pattern

out := make(chan Item)
go func() {
	defer close(out)
	for _, item := range items {
		out <- item
	}
}()

Anti-pattern

• adding recover around close(ch) because ownership is unclear

Explanation: This anti-pattern is tempting because it suppresses panics, but it hides a lifecycle bug instead of fixing it.

Why

• channel shutdown is simple only when channel ownership is simple