Comment by messe

If you're going to immediately await it, you can just do

    saveFile(io, data, "saveA.txt");

EDIT: following up on that, I'm actually not sure that

    io.async(saveFile, .{io, data, "saveA.txt"}).await(io);

will even be valid code. Futures in this article are declared as var, meaning mutable. This appears to be because Future.await is going to take a pointer as its initial argument. However, because it's a temporary and therefore treated as const, the return value of io.async will not be passable to a .await function expecting a *Future as its initial argument without first being stored in a mutable var.

So this would be valid:

    var save_future = io.async(saveFile, .{io, data, "saveA.txt"});
    save_future.await(io);

But the original presented in the parent comment would be equivalent to the following, and therefore invalid:

    const save_future = io.async(saveFile, .{io, data, "saveA.txt"});
    save_future.await(io); // compile error