asio::io_context io_context;
 
  testWait tc;
  steady_timer timerTest(io_context);
  {
    
      timerTest.expires_after(std::chrono::seconds(600));
      
     
      timerTest.async_wait(std::bind(&testWait::waitHandle, &tc,std::placeholders::_1));
      timerTest.async_wait(std::bind(&testWait::waitHandle2, &tc));
      
      timerTest.expires_after(std::chrono::seconds(30));  //這個(gè)調(diào)用會(huì)導(dǎo)致timerTest中原先已經(jīng)在異步等待的回調(diào)被立即調(diào)用（下一個(gè)事件循環(huán)）并且回調(diào)函數(shù)errorcode不為0，其實(shí)就是會(huì)先調(diào)用cancel函數(shù)
      timerTest.async_wait([](const std::error_code& ec) {
          if (!ec)
          {
              std::cout << "lambda wait" << std::endl;   //30秒后調(diào)用
          }
          else
          {
              std::cout << "lambda err code:" << ec.value() << " what" << ec.message() << std::endl;
          }
          }
          );
  }