async iterable merge function that ends upon the first "done"

[jasonkuhrt]

I am looking for an async iteratable combinator like merge, with the different that instead of waiting for all the iterables that were merged to complete, wait until one of the iterables completes.

I checked the source code and combinators therein, but it seems this is not readily available.

I also don't see an easy way to build up such a combinator from the existing set.

[trxcllnt]

This would be doable if we had materialize() and dematerialize() @mattpodwysocki