The Go Team has actually communicated this matter extensively through your blog (https://blog.golang.org/v2-go-modules).
The problem is that the official solution, as mentioned in the article, seems really bad... you just have to copy the whole project into the `v2` folder, then do the same for a future `v3` and so on... it kind of goes against normal practices of using version control tools for this kind of thing, where each version would be in a different branch, not folder.
Not to mention having duplicate files like this can make finding files in your editor a bit confusing as well.
Though I like how Go solved dependency management and dared to go on a different path than almost every other package manager, this particular solution seems to go a bit too far?!
I mean, it goes against how got works. SVN does the branch-in-a-folder thing, so it's not anathema to "version control".
That said, as for branch-in-a-folder, "thanks, I hate it".