message: fix unit test (at least on linux)
diff: @@ -215,6 +215,7 @@ fn test_watch(directory: &mut dyn Directory) {
  assert!(directory
  .atomic_write(Path::new("meta.json"), b"random_test_data_2")
  .is_ok());
  + assert_eq!(receiver.recv_timeout(Duration::from_millis(500)), Ok(i));
  assert!(i + 1 <= counter.load(SeqCst)); // notify can trigger more than once.
  }
  mem::drop(watch_handle);
  