I think it would be nicer if clients to this method created the ray object themselves, and then called ray.FindIntersection() on it. Something like:

    ray := physics.NewRay(pos, look)
    hitSpot, index := ray.FindAnyIntersect(world, players)

The name FindAnyIntersect is probably terrible, but I couldn't think of anything better that would allow the creation of e.g. a FindBoxIntersect() method or a FindWorldIntersect() method in a logical way.

We should probably also move this to the physics package, which should be easy, since it doesn't look like it depends on anything in server/.