Function eventuals::join

pub fn join<J>(joinable: J) -> Eventual<J::Output> where
    J: Joinable, 

An eventual that will only progress once all inputs are available, and then also progress with each change as they become available. For example, join(([“a”, “b, “c”], [1, 2, 3])) may observe something like [(“a”, 1), (“a”, 2), (“c”, 2), (“c”, 3)] or [(“c”, 1), (“c”, 3)]. The only snapshot that is guaranteed to be observed is (“c”, 3).