Dart: 08 Desafio: seu futuro ainda não está escrito

import 'dart:io';

void main() async {

  String messager = '';

  print('------- INICIADO CHAT  -------');
  await clock(3);
  print('------- CHAT ENTRE EVERTON E LUANA INICIADO  -------');
  await clock(1);
  print('Everton Inicia a Conversa com Luana');

  try{
      var by = true;
      String conversationEvertonAndLuana = '';
      String messager = '';

    do{
      messager = messageEvertonFunc();
      await clock(2);
      print('-- TELA CHAT LUANA --');
      conversationEvertonAndLuana += messager;
      print(conversationEvertonAndLuana);
      print('----------------------------- \n LUANA RESPONDE: ');
      
      if(messager.contains('xau') || messager.contains('Xau')){
        by = false;
        break;
      }

      messager = messageLuanaFunc();
      await clock(2);
      print('-- TELA CHAT EVERTON --');
      conversationEvertonAndLuana += messager;
      print(conversationEvertonAndLuana);
      print('----------------------------- \n EVERTON RESPONDE: ');

      if(messager.contains('xau') || messager.contains('Xau')){
        by = false;
      }
    }while(by);

  }catch(e){
    print('unexpected error: $e');
  }finally{
    await clock(1);
    print('CONVERSA ENCERRADA');
    await clock(3);
  }

}

String messageEvertonFunc(){
  String nameEverton = ' \n Everton: ';
  String message = stdin.readLineSync().toString();
  String messageSend = nameEverton + message;

  return messageSend;
}

String messageLuanaFunc(){
  String nameLuana = '\n Luana: ';
  String message = stdin.readLineSync().toString();
  String messageSend = nameLuana + message;

  return messageSend;
}

Future clock(int seconds){
  return Future.delayed(Duration(seconds: seconds));
}