pub fn try_select<A, B>(future1: A, future2: B) -> TrySelect<A, B>
where
    A: TryFuture + Unpin,
    B: TryFuture + Unpin,
{
    super::assert_future::<Result<EitherOk<A, B>, EitherErr<A, B>>, _>(TrySelect {
        inner: Some((future1, future2)),
    })
}
Waits for either one of two differently-typed futures to complete.

This function will return a new future which awaits for either one of both
futures to complete. The returned future will finish with both the value
resolved and a future representing the completion of the other work.

Note that this function consumes the receiving futures and returns a
wrapped version of them.

Also note that if both this and the second future have the same
success/error type you can use the `Either::factor_first` method to
conveniently extract out the value at the end.

# Examples

```
use futures::future::{self, Either, Future, FutureExt, TryFuture, TryFutureExt};

// A poor-man's try_join implemented on top of select

fn try_join<A, B, E>(a: A, b: B) -> impl TryFuture<Ok=(A::Ok, B::Ok), Error=E>
where A: TryFuture<Error = E> + Unpin + 'static,
B: TryFuture<Error = E> + Unpin + 'static,
E: 'static,
{
future::try_select(a, b).then(|res| -> Box<dyn Future<Output = Result<_, _>> + Unpin> {
match res {
Ok(Either::Left((x, b))) => Box::new(b.map_ok(move |y| (x, y))),
Ok(Either::Right((y, a))) => Box::new(a.map_ok(move |x| (x, y))),
Err(Either::Left((e, _))) => Box::new(future::err(e)),
Err(Either::Right((e, _))) => Box::new(future::err(e)),
}
})
}
```
futures-util/src/future/try_select.rs