Where did all the goblins go?

[Sardy]

Forgive me if this has been covered before, or if there's an explanation in the books that I somehow missed?

At the end of the Third Age, after the defeat of Sauron, what became of all the goblins and orcs? Were they bound to Sauron and the ring, and so faded after its destruction? Did they retreat to the deep places of the earth, never to be heard from again? Did they become second-class citizens?

I'm curious whether their fate was ever addressed...