Comment by aric

It is to prevent hash tables being relied on for order. Randomization was added so maps aren't treated as invariant. The behavior in a range of a map is no less correct to be changing (in Go) rather than unchanging (in other languages). In other words, invariant relative to what? It's not too important. It's one of numerous ways Go promotes clearer design, at least in my eyes, to have disorder represent unordered and order represent ordered.