Golang (GO) is another high-level programming language. It's usually used to make backend stuff.
Backend stuff, I mean, for example rest API for your website, CMS for your website or chatbot. But, as it always is, the community made a lot of frameworks based on Golang, for example, A framework to use Golang as a frontend language (ex. Buffalo).
Golang is a statically typed compiled language in the tradition of C, but with some more features. Overall, Go's syntax is similar to C's syntax.
That features as I said are for example:
Tools for Golang, compiler and source code of Golang are free and open-source.
If you want to see the full list of Golang libraries, packages, and stuff, you can see it here.
The file extension for Golang is .go