== Promises

<<promise, Promises>> are the recommended default coroutine type.
They're eager and thus easily usable for ad-hoc concurrecy.

[source,cpp]
----
cobalt::promise<int> my_promise()
{
   co_await do_the_thing();
   co_return 0;
}

cobalt::main co_main(int argc, char * argv[])
{
    // start the promise here
    auto p = my_promise();
    // do something else here
    co_await do_the_other_thing();
    // wait for the promise to complete
    auto res = co_wait p;

    co_return res;
}
----