The await keyword in #godot4 is the single most exciting feature I think I've ever encountered in a language or engine.

Being able to trivially turn any function into a slow-running asynchronous subroutine simplifies SO MUCH. Before, my every-game-loop processes would have to handle hanging out and waiting to progress through various states. Now? Simply kick back and await.

I don't know if engines besides #godot have something similar, but I can't imagine ever going back to life without it.