Creating vendor directories directly in srcs of go and rust packages so fixed output derivations won't be needed

I see. There’s another topic which seems related now, which is “importing from derivation” which hydra doesn’t yet support: Import From Derivation - NixOS Wiki & Is importing a derivation from another repository bad practice?

If hydra was able to import from a derivation, it would have been possible to create a deps.nix inside the $src of go modules projects, and then import it?