Adding this would be a nice compliment to aclosing(), which was already merged for 3.10.

Otherwise, witness the ugliness of using aclosing() with an async iterable object:

    async with aclosing(foo.__aiter__()) as agen:
        async for item in agen:
            ...

I'd like:

    async with aclosing(aiter(foo)) as agen:
        async for item in agen:
            ...