I can't tell you how many time global dependencies in python have cause me headaches. Do a small project then do another small project 6 months later and the formers dependencies conflict with the latter's.
The whole concept of "only one major version of library can be installed at a time" is completely broken and is the direct cause of diamond import issues. Go designers have correctly recognized that two major versions of a library are actually two different libraries, only under the same name and the same team.
The "v2/ subdirectory" practice of versioning Go packages is one of the things I love the most about Go. Combined with the "packages are directories" philosophy, it makes it easy to use as many major versions of the library as you want, without any complications whatsoever.
It's such a nightmare for internal scripts. Even for ruby shops where theoretically bundler solves the problem there's all these cowboys with ten external dependencies and no lockfile
