Resolve race condition and ensure t.Error is not called from goroutine.

client_test.go

@@ -31,15 +31,27 @@ func TestCustomConnectionFunction(t *testing.T) {
 	netClient, netServer := net.Pipe()
 	defer netClient.Close()
 	defer netServer.Close()
-	var firstMessage = ""
+
+	outputChan := make(chan struct {
+		msg []byte
+		err error
+	})
 	go func() {
 		// read first message only
 		bytes := make([]byte, 1024)
+		netServer.SetDeadline(time.Now().Add(time.Second)) // Ensure this will always complete
 		n, err := netServer.Read(bytes)
 		if err != nil {
-			t.Errorf("%v", err)
+			outputChan <- struct {
+				msg []byte
+				err error
+			}{err: err}
+		} else {
+			outputChan <- struct {
+				msg []byte
+				err error
+			}{msg: bytes[:n]}
 		}
-		firstMessage = string(bytes[:n])
 	}()
 	// Set custom network connection function and client connect
 	var customConnectionFunc OpenConnectionFunc = func(uri *url.URL, options ClientOptions) (net.Conn, error) {
@@ -52,10 +64,16 @@ func TestCustomConnectionFunction(t *testing.T) {
 
 	// Try to connect using custom function, wait for 2 seconds, to pass MQTT first message
 	if token := client.Connect(); token.WaitTimeout(2*time.Second) && token.Error() != nil {
-		t.Errorf("%v", token.Error())
+		t.Fatalf("%v", token.Error())
+	}
+
+	msg := <-outputChan
+	if msg.err != nil {
+		t.Fatalf("read from simulated connection failed: %v", msg.err)
 	}
 
 	// Analyze first message sent by client and received by the server
+	firstMessage := string(msg.msg)
 	if len(firstMessage) <= 0 || !strings.Contains(firstMessage, "MQTT") {
 		t.Error("no message received on connect")
 	}