[junke]

Just to nitpick, that is 4 lines because you add a type too. Also, I noticed this in controller.go:

        // Unreachable based on the rules of there not being duplicate
	// environments of the same name for the same owner, but return false
	// instead of panicing.
	return false

Guess what, I worked with a sort function with the same kind of assumptions, but the implicit rules was broken: the "should never happen" path happened (names were not unique, after all). I found about that only after I wrote my own sort which was careful enough to check that the order was indeed total and when results diverged for some tests. I really disliked that because sorting was an important part in that tool (maybe it is not in yours).