My initial reaction was that I'd use a map like one of the parent posters said. But instead of creating a Set we can just use a map[type]bool, which is essentially a Set.

Incidentally, I just wrote a Unique method today for a specific array.

      type Elements []Element
      func (es Elements) Uniq() []Element {
          seen := make(map[Element]bool, 0)
          results := make([]Element,0)
          for _,e := ranges es {
              if seen[e] {
                  continue
              }
              seen[e] = true
              results = append(results, e)
          }
          return results
      }

I did not think about performance all that much, but map lookup is pretty good and I iterate through the array one time.

(As a side-note, we know that the size will be below 100 so it's not perf critical)

EDIT: Wording EDIT2: To address one of your points, you could probably just create a hash yourself and use that as the map Key as well, as you have said.