Something I've wanted was a way of setting up any computer I touch to have what I want/expect it to have so I can start working in a dev environment.

I dev on windows, osx, and Ubuntu.

So far I've written a go CLI that is able to bootstrap some stuff for a fresh computer, and tell me what I'm missing.

Have you tried Nix[1]? The learning curve was a bit steep for me, but I think I finally started "getting" it and it absolutely solves this problem for me. Now I'm at the point where if I install Nix on any computer, VM, whatever, I can just pull in my configs via home manager[2] and everything Just Works. It's seriously one of the best package managers I've ever used, and I can't imagine going back to anything else. Windows support is only via WSL, so this might be a non-starter for you.

[1]: https://nixos.org/

[2]: https://github.com/nix-community/home-manager