readByWait method
Implementation
Future<BleMessage> readByWait(String serviceUuid,String characteristicUuid) async{
Completer<BleMessage> bleReadResultCompleter = Completer();
_temporaryCompleter[characteristicUuid]=bleReadResultCompleter;
_channel.invokeMethod("read",{"serviceUuid":serviceUuid,"characteristicUuid":characteristicUuid});
return await bleReadResultCompleter.future;
}