But GOPATH is deprecated so you shouldn't be relying on that anymore anyway.
The expectation is that the user just clones your Git repo to _anywhere_ on their PC and runs `go test` there. If they want to consume this local development version in their application then they use a simple `replace` directive in their go.mod to point their dependency at their local version.
If they're still using GOPATH then that's something they can probably manage themselves honestly. That's just a simple folder move. It's been like, what, nearly 2 years since GOPATH was deprecated?