Whenever I read any press about actors or goroutines, they say the same thing about preventing races (and the need for explicit locking) through share-nothing concurrency.

It's easy to scatter the computations, but they never go on to explain how to gather them back up.

You're going to render one frame to the screen. Did multiple actors have a write-handle into the frame buffer? What about collisions, does each entity collide with itself, without sharing position information with other actors?