go runtime_error ai_generated true

fatal error: all goroutines are asleep - deadlock! (context cancellation not propagated)

ID: go/goroutine-context-cancel-not-propagated

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2025-02-20First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.20 active — — —
1.21 active — — —

Root Cause

A parent goroutine cancels a context but child goroutines are not listening to the context's Done channel, causing them to block indefinitely.

generic

中文

父协程取消上下文，但子协程未监听上下文的 Done 通道，导致它们无限阻塞。

Workarounds

  1. 95% success Use select to listen on context.Done() in blocking operations. 
    select {
case result := <-ch:
    return result
case <-ctx.Done():
    return ctx.Err()
}
  2. 90% success Pass context to functions and check cancellation periodically. 
    func worker(ctx context.Context) error {
    for {
        select {
        case <-ctx.Done():
            return ctx.Err()
        default:
            // do work
        }
    }
}

Dead Ends

Common approaches that don't work:

  1. Only checking context.Err() without using select on Done. 80% fail

    context.Err() is only set after cancellation; without select, goroutine may not wake up.

  2. Passing context by value but not using it in select. 70% fail

    The context is available but not used to unblock the goroutine.