Now that you have hopefully digested the Go Fundamentals section you have a solid grounding of a majority of Go's language features and how to do TDD.
This next section will involve building an application.
Each chapter will iterate on the previous one, expanding the application's functionality as our product owner dictates.
New concepts will be introduced to help facilitate writing great code but most of the new material will be learning what can be accomplished from Go's standard library.
By the end of this you should have a strong grasp as to how to iteratively write an application in Go, backed by tests.