Go is a modern, generic-purpose, open source programming language that was officially announced at the end of 2009. Go began as an internal Google project, which means that it was started as an experiment, and has since been inspired by many other programming languages, including C, Pascal, Alef, and Oberon. Go's spiritual fathers are the professional programmers Robert Griesemer, Ken Thomson, and Rob Pike.
They designed Go as a language for professional programmers who want to build reliable, robust, and efficient software. Apart from its syntax and its standard functions, Go comes with a pretty rich standard library.
At the time of writing, the latest stable Go version is version 1.13. However, even if your version number is higher, the contents of the book will still be relevant.
If you are going to install Go for the first time, you can start by visiting https://golang.org/dl/. However, there is a big chance that your UNIX variant has a ready-to-install package for the Go programming language, so you might want to get Go by using your favorite package manager.