When developing a new blockchain, we as a team chose Go lang over Java and other candidates, due to Go being (a) natively suited to concurrency - there are primitives in the language itself (goroutines, channels) that really help with reasoning about concurrency (b) super fast - build time, running, testing are all much faster that Java, this gives a far superior developer experience (c) shorter and stricter than Java - code is much shorter (less verbose), and there is usually one good way to do things, and even the code formatter that is bundled with Go is very opinionated - over a short time this makes reading other people's code far smoother than having to deal with different styles.

You should be aware that Go presently (v1.13) lacks Generics.

Node.js has been growing in popularity, and the ability to access the global pool of Javascript developers is great. There is a decreased amount of effort for people to work across the frontend and backend, and the language itself is easy and works well for many common use cases.

Go was the other serious candidate, but it just hasn't been implemented in as many Production systems yet, and the best Go engineers I've known have been hackers, whereas we're building a robust analytics platform that requires more caution. Type safety is easily added with TypeScript, and NPM is awesomely handy.

When I was evaluating languages to write this app in, I considered either Python or JavaScript at the time. I find Ruby very pleasant to read and write, and the Ruby community has built out a wide variety of test tools and approaches, helping e deliver better software faster. Along with Rails, and the Ruby-first Heroku support, this was an easy decision.