awaitAll

fun <T, U> awaitAll(future1: PNFuture<T>, future2: PNFuture<U>): PNFuture<Pair<T, U>>
fun <T, U, X> awaitAll(future1: PNFuture<T>, future2: PNFuture<U>, future3: PNFuture<X>): PNFuture<Triple<T, U, X>>