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.
