Function async_wait

include/boost/asio/basic_signal_set.hpp:601–609

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

private:
  // Disallow copying and assignment.