go runtime_error ai_generated true

panic: runtime error: send on closed channel (context cancellation)

ID: go/context-cancellation-ignore

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-09-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.7 active — — —
1.23 active — — —

Root Cause

When a context is cancelled, its channel is closed; sending on it causes a panic.

generic

中文

当上下文被取消时，其通道被关闭；向其发送数据会导致恐慌。

Workarounds

  1. 95% success Use select with context.Done() to avoid sending on closed channel 
    select {
case ch <- data:
case <-ctx.Done():
    return ctx.Err()
}
  2. 90% success Create a new channel for each operation and close it safely 
    ch := make(chan int, 1)
select {
case ch <- data:
case <-ctx.Done():
    close(ch)
    return ctx.Err()
}

Dead Ends

Common approaches that don't work:

  1. Checking context.Err() before send but not handling race condition 70% fail

    Context can be cancelled between check and send.

  2. Using a separate channel that is not closed on cancellation 60% fail

    Ignores the cancellation signal, leading to resource leaks.