All I wanted was a way to safely and easily cleanup my $GOPATH. I don't have a lot disk space and $GOPATH takes up most of it.

This thing apparently doesn't solve my problem. `go mod tidy` simply removes a dependency from a module, but that dependency is still cached in a big arcane directory at $GOPATH/src/mod. Why?

I think we all should be using something like Nix for dependency management that solves all problems, but that is so hard to setup!

And sadly, to use. Nix is a great idea but it could do a lot to help itself out if it ever wants to become more than niche:

1. Use a more approachable package definition language; Starlark (https://github.com/google/starlark-go) or Lua would probably be great choices.

2. Make it reasonable to figure out what the "type" of a package dependency is so we can figure out how to use it and/or find its source code

3. Document package definitions. We document source code in typed languages; Nix expression language is untyped and generally less readable--why not document it?

4. Nix tools have a `--help` flag that only ever errors with "cannot find manpage". This is just user-hostile.

5. Using almost-JSON for the derivation syntax, but then providing a "pretty printer" that keeps everything on one line but with a few more space characters.

6. Horrible build output--everything for every build step (megabytes of useless gcc warnings) gets dumped to the screen. Contrast that with Bazel and company which only print errors.

Plus a long tail of other things I'm forgetting.