go io_error ai_generated true

fatal error: concurrent file writes (log file)

ID: go/goroutine-racy-file-write

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2025-10-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.0 active — — —
1.22 active — — —

Root Cause

Multiple goroutines writing to the same file without synchronization, causing corrupted output.

generic

中文

多个协程同时写入同一个文件而没有同步，导致输出损坏。

Workarounds

  1. 95% success Use a mutex to serialize file writes 
    var mu sync.Mutex
f, _ := os.Create("log.txt")
mu.Lock()
f.Write([]byte("data"))
mu.Unlock()
  2. 90% success Use a dedicated goroutine to handle all writes via channel 
    ch := make(chan string)
go func() {
    f, _ := os.Create("log.txt")
    defer f.Close()
    for s := range ch {
        f.WriteString(s)
    }
}()
ch <- "log entry"

Dead Ends

Common approaches that don't work:

  1. Using os.File.Write directly without lock 90% fail

    File writes are not atomic; interleaved writes corrupt data.

  2. Using bufio.Writer without synchronization 80% fail

    Bufio.Writer buffers writes but still racy when flushing.