Adding a type system to an existing language that was never intended to have that type system is not simple. And in Go, the language seems designed to largely eject its type system at the earliest opportunity that doesn't negatively impact the compiler. This will naturally constrain the capabilities of the generic programming constructs, much as it did in Josh Bloch's Java generics implementation.

Go is going to be torn between the minimalism of its creators, and the desires for modern capabilities expressed by its vocal user base. If this were a movie, it would be "A Beautiful Mind".