messageReceiveStream method Null safety
- {String? channelUrl}
Returns a stream to listen new messsage event with given channelUrl.
It will be triggered every new message if channelUrl is not provided
Implementation
Stream<BaseMessage?> messageReceiveStream({String? channelUrl}) async* {
  if (currentUser == null) throw ConnectionRequiredError();
  await for (final res in _int.streamManager.msgReceived.stream) {
    if (channelUrl != null) {
      if (res.channel.channelUrl == channelUrl) yield res.message;
    } else {
      yield res.message;
    }
  }
}