#### co_spawn (1 of 6 overloads)

Spawn a new coroutined-based thread of execution.

    template<
        typename Executor,
        typename T,
        typename AwaitableExecutor,
        typename CompletionToken = DEFAULT>
    DEDUCED co_spawn(
        const Executor & ex,
        awaitable< T, AwaitableExecutor > a,
        CompletionToken && token = DEFAULT,
        constraint_t<(is_executor< Executor >::value||execution::is_executor< Executor >::value) &&is_convertible< Executor, AwaitableExecutor >::value >  = 0);

###### Parameters

ex

  The executor that will be used to schedule the new thread of execution.

a

  The `awaitable` object that is the result of calling the coroutine's entry point function.

token

  The completion token that will handle the notification that the thread of execution has completed. The function signature of the completion handler must be:

      void handler(std::exception_ptr, T);

###### Completion Signature

    void(std::exception_ptr, T)

###### Example

    asio::awaitable<std::size_t> echo(tcp::socket socket)
    {
      std::size_t bytes_transferred = 0;

      try
      {
        char data[1024];
        for (;;)
        {
          std::size_t n = co_await socket.async_read_some(
              asio::buffer(data), asio::use_awaitable);

          co_await asio::async_write(socket,
              asio::buffer(data, n), asio::use_awaitable);

          bytes_transferred += n;
        }
      }
      catch (const std::exception&)
      {
      }

      co_return bytes_transferred;
    }

    // ...

    asio::co_spawn(my_executor,
      echo(std::move(my_tcp_socket)),
      [](std::exception_ptr e, std::size_t n)
      {
        std::cout << "transferred " << n << "\n";
      });

###### Per-Operation Cancellation

The new thread of execution is created with a cancellation state that supports `cancellation_type::terminal` values only. To change the cancellation state, call `this_coro::reset_cancellation_state`.