go runtime_error ai_generated true

panic: send on closed channel

ID: go/channel-send-on-closed-channel

Also available as: JSON · Markdown · 中文
80%Fix Rate
90%Confidence
0Evidence
2024-02-11First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.0+ active — — —

Root Cause

A goroutine executed ch <- val after another goroutine called close(ch). Sending on a closed channel always panics; the race between sender and closer is the root issue.

generic

中文

某个 goroutine 在另一个 goroutine 调用 close(ch) 之后仍执行 ch <- val。向已关闭 channel 发送数据必定 panic，发送方与关闭方之间的竞态是根本原因。

Workarounds

  1. 95% success 
    done := make(chan struct{})
// producer owns close
func producer(ch chan int, done <-chan struct{}) {
    defer close(ch)
    for i := 0; ; i++ {
        select {
        case <-done:
            return
        case ch <- i:
        }
    }
}
  2. 90% success 
    select {
case ch <- v:
case <-quit:
    return
}

Dead Ends

Common approaches that don't work:

  1. 90% fail

    recover only stops the panic in the current goroutine; the send is logically invalid and the message is silently lost, corrupting downstream logic. Also recover does not work across goroutine boundaries.

  2. 85% fail

    Sleep does not establish happens-before ordering; the scheduler may still run the closer after the sender. It only narrows the race window and fails under load.