fix go race bug

[WIZARD-CXY]

I'm using consul as part of my program, when I enable -race in the go test, I found this small bug, since w.buf = append(w.buf, p2) can be a write operation.

[slackpad]

Hi @WIZARD-CXY thanks for the PR!

I think the read lock was intended to not synchronize writers after the flush was done (since there's no way to set flush to false again, and after startup it will basically be going through that path forever). You are right there's a race here, though. I think this fix would have the intended behavior:

func (w *GatedWriter) Write(p []byte) (n int, err error) {
        // Once we flush we no longer synchronize writers since there's
        // no use of the internal buffer. This is the happy path.
        w.lock.RLock()
        if w.flush {
                w.lock.RUnlock()
                return w.Writer.Write(p)
        }
        w.lock.RUnlock()

        // Now take the write lock.
        w.lock.Lock()
        defer w.lock.Unlock()

        // Things could have changed between the locking operations, so we
        // have to check one more time.
        if w.flush {
                return w.Writer.Write(p)
        }

        // Buffer up the written data.
        p2 := make([]byte, len(p))
        copy(p2, p)
        w.buf = append(w.buf, p2)
        return len(p), nil
}

[WIZARD-CXY]

Perfect! I will change according to your suggestion

[WIZARD-CXY]

@slackpad PTAL

[WIZARD-CXY]

@slackpad PTAL thx

[slackpad]

Thanks!