example.dart

gistfile1.dart

main() async {
  final broadcaster = StreamController.broadcast();
  broadcaster.stream
      .asyncExpand((data) =>
          Stream.fromFuture(Future.delayed(Duration(seconds: 10), () {
            return data;
          })))
      .listen((onData) {
        print(onData);
  });
  broadcaster.add("123");
  broadcaster.add("121");
  broadcaster.add("128");
}