go(ing) under

Lots of people like go and this year I began to find it unavoidable - I'm even ending the year with go being the main language that helps pay my bills!

One of the things that go lets you do is pass functions around.
I started the year talking about under from the j language. Which lets you 'bookend' some function with another function (a verb) and a function which undoes that function (obverse).
A great example is Pythagoras' theorem:

1. You perform some 'pre-processing' on each value (squaring)
2. You add all the values up
3. You square root the result

I started the year talking about under in clojure. Here it is implemented in go. Complete with functions being passed around, closures, and functions returning functions. Happy new year!