Spawn a new thread of execution.

template<
    typename Executor,
    typename F,
    typename CompletionToken>
DEDUCED co_spawn(
    const Executor & ex,
    F && f,
    CompletionToken && token,
    typename enable_if< is_executor< Executor >::value >::type *  = 0);

The entry point function object f must have the signature:

awaitable<void, E> f();

where E is convertible from Executor.