This seems like bad advice. I've very rarely committed extra files by accident, but I would 100% forget to unignore files I meant to commit. If you're doing an initial setup step to gitignore everything, why not just do an initial setup step to gitignore the usual files? Make a template that you copy into all of your repos.
Maybe that's more ergonomic than forcing all users to learn about ~/.gitignore or manually adding .DS_Store *.sav~ et cetera into your Go project's repo's .gitignore.