go runtime_error ai_generated true

fatal error: all goroutines are asleep - deadlock! (nil channel receive)

ID: go/channel-receive-from-nil-channel

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-09-03First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.0+ active — — —

Root Cause

A goroutine attempted to receive from a nil channel, which blocks forever. If all goroutines are blocked on nil channels, the runtime detects a deadlock.

generic

中文

某个 goroutine 尝试从 nil channel 接收数据，这会永久阻塞。如果所有 goroutine 都阻塞在 nil channel 上，运行时会检测到死锁。

Workarounds

  1. 98% success 
    ch := make(chan int)
// or ch := make(chan int, 1)
  2. 90% success 
    select {
case v := <-ch:
    // use v
case <-time.After(1 * time.Second):
    return errors.New("timeout: channel may be nil")
}

Dead Ends

Common approaches that don't work:

  1. 90% fail

    A nil channel is not the same as an uninitialized variable; you must explicitly create it with make().

  2. 85% fail

    A select with a nil channel case will block if no other case is ready; default only helps if you want non-blocking behavior.