I like functions as first-class values and closures. If they weren't present, I might well have bailed months ago. :) And from various experiences doing OO with other languages, I can kindof buy that Go interfaces are often 80% of what you want.

Most of what I've been working on is a Rest API. Here's an example of a problem that felt like it should be something for which I'd be able to write an abstraction to deal with, but turned out to be challenging, at least as a n00b:

https://groups.google.com/forum/#!topic/golang-nuts/JhsiiGHQ...

(Incidentally, though I moved past my then really poor understanding of Go interfaces, I wasn't able to apply the respondent's answer or my new general knowledge to achieve the abstraction I was looking for, and settled for just grinding out the same code for the dozen entities/endpoints it applied to.)

Concurrency: I suspect there's a bit that's hidden in some libraries we're using, and we may yet need to write our own code for some API requests that get processed offline, but I haven't had to explicitly write code for it yet.

If you can think of a specific exercise that might serve to illustrate Go's outstanding concurrency strengths, I'd be interested to try it and compare efforts to another language or two.