The Java designers wanted jars to be runnable by any virtual machine, ever. This meant preserving some pretty old and nasty hacks (like erasure for generics) to allow old jars to work with new virtual machines.

With Go, you would just recompile and that would be it. Go doesn't even support loadable modules yet (although it's coming soon), so they can do whatever they want with compat. It's unlikely they'll make the same mistakes Java did because they are not blinded by the "write once, run anywhere" ideology.