Function reenter

example/cpp20/operations/composed_8.cpp:129–153

      ) mutable
      {
        reenter (coro)
        {
          while (repeat_count > 0)
          {
            --repeat_count;

            delay_timer->expires_after(std::chrono::seconds(1));
            yield delay_timer->async_wait(std::move(self));
            if (error)
              break;

            yield boost::asio::async_write(socket,
                boost::asio::buffer(*encoded_message), std::move(self));
            if (error)
              break;
          }

          // Deallocate the encoded message and delay timer before calling the
          // user-supplied completion handler.
          encoded_message.reset();
          delay_timer.reset();

          // Call the user-supplied handler with the result of the operation.
          self.complete(error);
        }
      },
      token, socket);
}