After reading this book, you should have a good idea of what packages are available in the standard library and how versatile Go can be out of the box. You should feel comfortable using Go for a variety of tasks, from simple tasks, such as working with files and making a network connection, to more advanced tasks, such as scraping websites and capturing packets. I also hope you gleaned some tips for writing idiomatic Go code.
The example programs provided should serve as references for building your own tools. Many of the programs are useful as-is and can be incorporated into your toolkit immediately, while a few are meant only to serve as a reference to help you perform common tasks.