Fix: use actual repo/package/version to do go mod init

[hsanjuan]

The build process:

• Sets a custom GOPATH
• Clones the repo we want to build inside it
• Does a go mod init and requires the repository we want to build directly (ignoring submodules) by doing a "rev-parse HEAD" on what we cloned
• Then go-builds the package "go build [...] -mod=mod my.package/abc.

I'm not sure why -mod=mod is updated, but this automatically updates the go.mod when working with submodules (sub-packages) that are tagged separately, to the point that it uses wrong releases (not the checked out one).

This has not been noticed in 4 years because we usually build the last tagged version of things. It you attempt to build a submodule with their own tag while using a tag that is not the latest it will start misbehaving.

This attempts to require exactly what we are trying to build in the go.mod file.

[github-actions[bot]]

This change produced no new differences in built artifacts.