The way that multi-version Go works on openSUSE is through update-alternatives.
One aspect of this is a profile.d script that sets GOROOT= to the current
version. This means that changing the Go version will make GOROOT incorrect in
the current login session -- which results in broken builds and other fun
problems.

Zygmunt Krynicki pointed out that this is completely unnecessary -- each Go
compiler binary contains a correct GOROOT. So this explicit setting is the only
reason upgrades are broken. Removing it will fix the problem entirely.