There is an entire section on Go Packages and Modules later in the course.

You'll learn to create your own Packages and Modules, how to publish them on GitHub and how to import them in other Go applications. Modules is a new feature of Go, fully implemented in Go v1.13 (at the end of 2019). They are the unit of Go source code interchange and versioning.

However, I recommend you to first master general Go Programming before diving into Packages and Modules.