https://code.google.com/p/go-wiki/wiki/PackageManagementTool...
Last I checked godep, the only thing I didn't like was the weird things you had to do with your project layout, but the way ahead is promising (and maybe it's not so bad now). Certainly it's much better than gopkg.in.
Though I do agree. It would be nice to have this sort of tooling as part of the Go distribution.
FWIW, I have been using godeps and it seems nice so far. I'd definitely recommend taking a look.
Well, technically they are (whipped up a quick example): http://play.golang.org/p/e2qkKN4VY1
But it requires the use of interface{}, which reduces the usefulness of the type system, and you still can't do (what I guess must be crazy) stuff like return a slice.