send method Null safety

Implementation

Future<WsEvent?> send(WsRequest request) async {
  if (appState.currentUser == null) {
    //NOTE: some test cases execute async socket data
    logger.e('sendCommand: connection is requred');
    throw ConnectionRequiredError();
  }

  try {
    await ConnectionManager.readyToExecuteWSRequest();
  } catch (e) {
    _ackTimers.remove(request.requestId)?.cancel();
    rethrow;
  }

  try {
    webSocket?.send(request.encoded);
  } catch (e) {
    _ackTimers.remove(request.requestId)?.cancel();
    rethrow;
  }

  final reqId = request.requestId;
  if (request.isAckRequired && reqId != null) {
    final timer = Timer(Duration(seconds: sdk.options.websocketTimeout), () {
      logger.e('sendCommand: did not receive ack in time');
      throw AckTimeoutError();
    });
    _ackTimers[reqId] = timer;

    final completer = Completer<WsEvent>();
    _completers2[reqId] = completer;
    return completer.future;
  } else {
    return null;
  }
}