I wonder if that's on purpose, to find bugs earlier. I know that the implementation of map in Go will intentionally shuffle the keys when you try to iterate over them, so that you never accidentally rely on insertion order.
It's very much on purpose, just like default maps being unordered. People should not rely on the ordering as it breaks the semantics of these features according to Go. It fits the Go philosophy well.
I've read somewhere (possibly when Go came out) that it's on purpose. For fun, Alan Cox once made a post on Google+ (RIP) showing a crappy random number generator based on Go's select.