Go seems really sensitive to this subject. Maps iterate in order, but one day they said “this is incidental and we said not to rely on it. You do, so we’re breaking it in a minor release” and now maps iterate in order… from a random offset

On the one hand, I never realized that map iteration order was consistent, but it's just the starting point that changes. On the other hand, I guess there's no other way to do it, since a proper shuffle would require O(n) bookkeeping. I suppose you could also flip a coin for going backwards too.