I normally read books and performs all examples hands on. Please keep in mind that I have computer science and mechatronics engineering background that allows me to speed-read these technical books.
I’m not sure whether the Astaxie has updated the book with Go module yet. It had been 5 years already. If he has not done it, you MUST ask questions about Go module after reading this: Using Go Modules - The Go Programming Language
This is because no one uses the old GOPATH way to implement Go package anymore aside maintaining legacy packages.
The rest of the books are merely to show how Go is used in different approaches and implementations. Astaxie integrates some 3rd-party packages and I would suggest you read the codes rather than blindly use it.