go runtime_error ai_generated true

panic: send on closed channel (from sender after close)

ID: go/goroutine-close-channel-from-sender

Also available as: JSON · Markdown · 中文
80%Fix Rate
86%Confidence
0Evidence
2024-11-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.0 active — — —
1.22 active — — —

Root Cause

Sender goroutine sends to a channel after another goroutine has closed it, often due to race.

generic

中文

发送者协程在另一个协程关闭通道后发送数据，通常由于竞态条件。

Workarounds

  1. 85% success Use a done channel to signal senders to stop 
    done := make(chan struct{})
ch := make(chan int)
go func() {
    for {
        select {
        case <-done:
            return
        case ch <- 1:
        }
    }
}()
close(ch) // but close done first
close(done)
  2. 90% success Use sync.WaitGroup to ensure all sends complete before close 
    var wg sync.WaitGroup
for i := 0; i < 5; i++ {
    wg.Add(1)
    go func() {
        defer wg.Done()
        ch <- 1
    }()
}
wg.Wait()
close(ch)

Dead Ends

Common approaches that don't work:

  1. Using recover() to catch panic and log 90% fail

    Recover doesn't fix the race; data may be lost.

  2. Checking channel length before send 95% fail

    len(ch) doesn't indicate closed state; send still panics.