go runtime_error ai_generated true

panic: send on closed channel

ID: go/send-on-closed-channel

Also available as: JSON · Markdown · 中文
80%Fix Rate
90%Confidence
0Evidence
2024-05-02First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.13 active — — —
1.21 active — — —

Root Cause

A producer goroutine sends to a channel that has already been closed by another goroutine (or by itself). Classic with fan-in patterns where a coordinator closes the channel too early.

generic

中文

生产者 goroutine 向已被其他 goroutine（或自身）关闭的通道发送数据。常见于协调者过早关闭通道的扇入模式。

Workarounds

  1. 93% success 
    select {
case ch <- v:
case <-ctx.Done():
    return
}
  2. 90% success 
    done := make(chan struct{})
go func() {
    defer close(ch)
    for {
        select {
        case <-done: return
        case ch <- next(): 
        }
    }
}()

Dead Ends

Common approaches that don't work:

  1. 80% fail

    A closed channel is always ready to receive; select will still pick the closed case and send panics.

  2. 55% fail

    Correct but often forgotten on one path; still panics if any send path bypasses the mutex, and adds contention.