Generic abs is an unrealistic toy example, sure. A much better example is an extensible array (a.k.a. vector a.k.a. list). This is the most basic data structure in all of programming, the first data structure needed in almost every program I write, and to be honest, I am of the opinion that a programming language that doesn't provide this has no reason to exist in the twenty-first century unless it was grandfathered in from the twentieth.
Fun enough, a list[0] in Go is actually a doubly linked list. Resizable slices[1] are built into the language. Though, this leads to C style coding that some people thing is annoying (assigning the result of append back to x, since it could allocate a new array).
