Color me unsurprised Marwan is on this issue. He and Aaron wrote Athens, Marwan wrote (to my knowledge) the first Go download protocol implementation that Athens is based on.
This issue is kind of curious because Athens already uses the go mod download -json command mentioned as a preflight check for module verification. More or less, if the repo passes the go module commands understanding of a module then Athens will serve it. In more verboten terms:
- a module version, pseudo version, or +incompatible must be able to be formulated
- that module (and it's dependencies) must produce a valid checksum
The checksum of modules just has to do with the current .mod and all files + recursively for each dependency. So, as the author pointed out you can have lots of space for arbitrary files by design so long as you have a basic go program.