go runtime_error ai_generated true

fatal error: all goroutines are asleep - deadlock! (unbuffered channel send without receiver)

ID: go/unbuffered-channel-deadlock-single-goroutine

Also available as: JSON · Markdown · 中文
80%Fix Rate
85%Confidence
0Evidence
2024-10-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.0 active — — —
1.1 active — — —

Root Cause

A goroutine tries to send on an unbuffered channel without a corresponding receiver ready, causing it to block forever. If all goroutines are blocked, the program deadlocks.

generic

中文

goroutine 尝试在无缓冲通道上发送，但没有相应的接收者准备好，导致其永远阻塞。如果所有 goroutine 都阻塞，程序将死锁。

Workarounds

  1. 95% success Ensure the receiver is ready before sending 
    ch := make(chan int)
go func() {
    val := <-ch
    fmt.Println(val)
}()
ch <- 42
  2. 90% success Use a select with a default case to make send non-blocking 
    select {
case ch <- 42:
default:
    fmt.Println("no receiver, dropping message")
}

Dead Ends

Common approaches that don't work:

  1. Using a buffered channel with size 1 to avoid blocking 85% fail

    A buffered channel can hold one value, but if the receiver never reads, the buffer will fill up and subsequent sends will block, leading to the same deadlock.

  2. Adding a time.Sleep before sending to wait for receiver 90% fail

    Sleep is unreliable; the receiver may not be ready in time, and it introduces unnecessary delays.