What this have to do with go modules? Any standard lib should have the ability add a new builtin module under a different namespace regardless of how third-party packages of managed, right?
The standard lib was considered core code and to make even the smallest change can have a huge impact. It was more a matter of, "if we're going to do a v2 language, what would we fix?" And, as it turns out this required no regression of existing core language code.
