I started to write one in the "Go 2 playground", but then realized they had that exact example in the draft design:

   func Keys(type K comparable, V interface{})(m map[K]V) []K {
    r := make([]K, 0, len(m))
    for k := range m {
     r = append(r, k)
    }
    return r
   }

Usage:

   m := map[int]int{1:2, 2:4}
   k := maps.Keys(m)
   // Now k is either []int{1, 2} or []int{2, 1}.

Well, you can :) https://play.golang.org/p/sum21uSy1Ae

For certain values of can.

Never said it was a good idea. It's inefficient, unsafe and hard to read but, as far as I can tell any generic function with concrete return types can be written using reflect (and any generic function with generic return types can be written also, it just requires the caller to manually cast from an interface{} to the correct type).

So, that's an interesting thing.

This is an awesome use of the reflect package!