client/pkg/transport: deflake TestWriteReadTimeoutListener

There is data race on `stop` channel. After verify write-timeout successfully,
the case won't wait for `blocker` to receive close signal from `stop` channel.
If the new `blocker`, which is to read-timeout verifier, get dial's result
immediately, the new `blocker` might fetch the message from `stop` channel
before old one and then close the connection, which causes that the
`conn.Read` returns `EOF` when it reads data.

How to reproduce this in linux devbox?

Use `taskset` to limit the test process in one-cpu.

```bash
cd ./client/pkg/transport
go test -c -o /tmp/test --race=true ./
taskset -c 0 /tmp/test -test.run TestWriteReadTimeoutListener -test.v -test.cpu 4 -test.count=10000 -test.failfast
```

To fix this, suggest to use seperate `stop` channel to prevent from data
race.

Signed-off-by: Wei Fu <fuweid89@gmail.com>

client/pkg/transport/timeout_listener_test.go

@@ -47,22 +47,23 @@ func TestWriteReadTimeoutListener(t *testing.T) {
 		writeTimeout: 10 * time.Millisecond,
 		readTimeout:  10 * time.Millisecond,
 	}
-	stop := make(chan struct{}, 1)
 
-	blocker := func() {
+	blocker := func(stopCh <-chan struct{}) {
 		conn, derr := net.Dial("tcp", ln.Addr().String())
 		if derr != nil {
 			t.Errorf("unexpected dail error: %v", derr)
 		}
 		defer conn.Close()
 		// block the receiver until the writer timeout
-		<-stop
+		<-stopCh
 	}
-	go blocker()
+
+	writerStopCh := make(chan struct{}, 1)
+	go blocker(writerStopCh)
 
 	conn, err := wln.Accept()
 	if err != nil {
-		stop <- struct{}{}
+		writerStopCh <- struct{}{}
 		t.Fatalf("unexpected accept error: %v", err)
 	}
 	defer conn.Close()
@@ -79,20 +80,21 @@ func TestWriteReadTimeoutListener(t *testing.T) {
 	case <-done:
 	// It waits 1s more to avoid delay in low-end system.
 	case <-time.After(wln.writeTimeout*10 + time.Second):
-		stop <- struct{}{}
+		writerStopCh <- struct{}{}
 		t.Fatal("wait timeout")
 	}
 
 	if operr, ok := err.(*net.OpError); !ok || operr.Op != "write" || !operr.Timeout() {
 		t.Errorf("err = %v, want write i/o timeout error", err)
 	}
-	stop <- struct{}{}
+	writerStopCh <- struct{}{}
 
-	go blocker()
+	readerStopCh := make(chan struct{}, 1)
+	go blocker(readerStopCh)
 
 	conn, err = wln.Accept()
 	if err != nil {
-		stop <- struct{}{}
+		readerStopCh <- struct{}{}
 		t.Fatalf("unexpected accept error: %v", err)
 	}
 	buf := make([]byte, 10)
@@ -105,12 +107,12 @@ func TestWriteReadTimeoutListener(t *testing.T) {
 	select {
 	case <-done:
 	case <-time.After(wln.readTimeout * 10):
-		stop <- struct{}{}
+		readerStopCh <- struct{}{}
 		t.Fatal("wait timeout")
 	}
 
 	if operr, ok := err.(*net.OpError); !ok || operr.Op != "read" || !operr.Timeout() {
 		t.Errorf("err = %v, want write i/o timeout error", err)
 	}
-	stop <- struct{}{}
+	readerStopCh <- struct{}{}
 }