Over the past few months, I've been working on a hobby project, which I've uncreatively called MyDailyStuff. It's written with Go on the backend and Typescript on the frontend (which I'll talk about in another post). Code for the site is available at my github profile.
I'll start with the summary of how I feel about Go. Basically, I'm glad it's gaining in popularity because I think it has a good chance of taking a lot of marketshare from NodeJS, which shouldn't be used nearly as much as it is. This isn't to say that Go is a perfect language, far from that. There have been numerous posts about the pros and cons of Go on Hackernews and the like, so I'll try to keep this focused on my experience building my application.
MyDailyStuff is a simple monolithic architecture. There's a REST API in Go and a TypeScript frontend single-page application. The datastore is ElasticSearch. Coming from a C# and JS background, the complete lack of OO design was jarring, but not too limiting for my usecase. Martini is a very capable microframework, very comparable to express. Based on what I've read online though, martini is full of "magic" and isn't very idiomatic, and is also on the slower side. For my usecase here I didn't notice any problems.
ElasticSearch wasn't too hard to integrate with, but I did have to heavily modify the elastigo source to do the queries I needed. I think with Go only having a year or so of major growth, a lot of the libraries are pretty nascent. Unfortunatley, there are probably a lot of missing/inadequate libraries for various tools with large APIs like ElasticSearch. My modifications still probably only covered a small fraction of the API, and I'll have to modify it some more to do highlighting.
Testing was relatively simple with Ginkgo, although I'm not a huge fan of mocha-style frameworks. I do like BDD-style testing, which is why I'm using Ginkgo, but I wish they would be more like mspec and not require you do the entire AAA in the "It" function. I tried out mocking with Testify, which requires you code to an interface. It is a bit awkward and tedious that you have to create an entire mock struct, but overall not too bad.
Overall, I'd recommend Go for most applications where NodeJS/Express is being considered, unless you need to do view isomorphism. Due to its simlicity, I can't recommend it for more advanced applications like data analysis of unstructured data. I'll probably end up using Go again in the future for other similar projects.