Git tags are completely orthogonal. When your main branch starts being v2, you only have to change go.mod to tack a v2 onto the end and keep your source code i

Git tags are completely orthogonal. When your main branch starts being v2, you only have to change go.mod to tack a v2 onto the end and keep your source code in the same place. "go get example.com/you/v2" will fetch exmaple.com/you from the main branch, read the go.mod file to see that it's v2, and continue. You don't have to actually create a v2 directory, or keep your old version in the main branch. (If you do tag releases, then "go get example.com/you/v2@v1.2.3" won't work, though.)