Or-done channel

Canonical guidance

• stop consuming input when cancellation makes more work irrelevant
• isolate cancellation plumbing in one wrapper instead of scattering repeated select logic
• keep wrapper ownership clear

Use when

• channel pipelines
• stream adapters
• cancellation-aware fan-in stages

Avoid

• ranging the input directly when the caller may stop early
• duplicating slightly different cancellation wrappers everywhere
• forgetting to close the wrapper output when it owns that output

Preferred pattern

• a wrapper goroutine relays values until either done closes or the input ends

Anti-pattern

• a pipeline stage that assumes the consumer will always drain every value

Explanation: This is tempting because demos often drain fully, but real callers often stop early.

Why

• abandoned reads are a common source of goroutine leaks