It's not about sorting, it's about every single abstract operation on a collection or other type of container. You either have to use primitives, or reimplement everything yourself on each new type. Most people just use primitives. This proliferation of primitives is what I actually dislike about reading and writing code in Go, but it's caused by not having a way to define abstract data types that work well.

There are a few good templating (gengen, genny, etc) solutions for generics in Go, but yeah, it would be nice if it was baked into the language.