Go expects to have all dependencies available at any time, downloading them from Internet if necessary. Cyclic dependencies are not a problem in that case because all dependencies are built together.

Packaging for a distro requires building Go packages isolated from the network in a chroot and having all the dependencies previously built in the same manner. So it is an iterative process, building blocks by building blocks. If you have a cyclic dependencies, you can't build iteratively, and you'll have to excise certain part of the code to eliminate the cycle.

They had to take it into an alley and kill it, mafia style.

More seriously, they probably means find ways to restructure packages and extract shared dependencies into subpackages to avoid cyclical dependencies.