Vinny You're tempting me to link the wikipedia article on async programming 😉.
You should describe more clearly what type of thing you want to achieve. That way it'd be easier to answer if it's doable in Godot or not.
There's a simple but sufficient thread api (threads, mutexes, semaphores). As I already said, you can set up a data streaming thread in a few lines of code.
I'm not sure what you mean by "pathfinder"? If you're talking about 2d navigation then yes. Godot has built-in helper objects that facilitate A* pathfinding, as well as navigation polygons pathfinding.