OP didn't say that code looks like ordinary sync code, only that it's possible to write code that works equally well for both sync and async. If you RTFA, it looks like this:

  var a = io.async(doWork, .{ io, "hard" });
  ...
  a.await(io);

If your `io` is async, this behaves like an async call returning a promise and then awaiting said promise. If `io` is sync then `io.async` will make the call immediately and `await` is a no-op.