OP here. There are a few projects that I wasn't able to work into the story that I think are worth a mention (though some of them are in that Awesome Terminals round-up linked in the article).

The Cobra library is a huge one: https://github.com/spf13/cobra

Other stuff worth a look includes:

Tmux: https://github.com/tmux/tmux Kitty: https://github.com/kovidgoyal/kitty Alacritty: https://github.com/alacritty/alacritty

I'm sure there's lots of other stuff I don't know about as well.