The two common patterns to forking a module are (1) forking via a separate repo or (2) vendoring, which forks all deps into the current module (or app). I recommend a third approach to forking using git subtree and go mod edit -replace. It’s very similar to repo forking without the repo

Let’s say you’ve made modifications to github.com/tj/go-spin. Once preserving changes in a repo is needed, use git subtree to move the fork into your monorepo, or app repo