Did not know about index-based string interpolation. Useful!
The part about changing a map while iterating is wrong though. The reason you may or may not get it is because go iterates in intentionally random order. It's nothing to do with speed. It's to prevent users from depending on the iteration order. It randomly chooses starting bucket and then goes in circular order, as well as randomly generates a perm of 0..7 inside each bucket. So if your edit goes into a bucket or a slot already visited then it won't be there.
Also, python is not an example to the contrary. Modifying python dicts while iterating is a `RuntimeError: dictionary changed size during iteration`