Function async_wait

include/boost/asio/basic_deadline_timer.hpp:656–664

      BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code))
        WaitToken = default_completion_token_t<executor_type>>
  auto async_wait(
      WaitToken&& token = default_completion_token_t<executor_type>())
    -> decltype(
      async_initiate<WaitToken, void (boost::system::error_code)>(
        declval<initiate_async_wait>(), token))
  {
    return async_initiate<WaitToken, void (boost::system::error_code)>(
        initiate_async_wait(this), token);
  }

private:
  // Disallow copying and assignment.