text: #include <iostream>
  #include <boost/asio.hpp>
  
  int main(int argc, char *argv[])
  {
      boost::asio::io_context io;
      boost::asio::steady_timer t(io, boost::asio::chrono::seconds(5));
      t.wait(); // synchronously, block 5 seconds.
      std::cout << "Hello, world!" << std::endl;
      return 0;
  }
  