Neat.
I like that you can add your own type specific functions.<p>I was interested in seeing the implementation of the Parallel Map, but on a quick browser through the source, could not find it.<p>If you're interested in other works in the same space, I think think the the Gen library (<a href="http://clipperhouse.github.io/gen/" rel="nofollow">http://clipperhouse.github.io/gen/</a>) goes a long way towards providing type-safe, idiomatic, Go code to achieve the same effects.