Add author and improve link. (#10404)

* add author

* Update the link which points to the free ebook instead of listing all books

books/free-programming-books-langs.md

@@ -809,7 +809,7 @@ Books on general-purpose programming that don't focus on a specific language are
 
 ### Go
 
-* [An Introduction to Programming in Go](http://www.golang-book.com)
+* [An Introduction to Programming in Go](https://www.golang-book.com/books/intro) - Caleb Doxsey
 * [Build Web Application with Golang](https://astaxie.gitbooks.io/build-web-application-with-golang/content/en/)
 * [Building Web Apps with Go](https://codegangsta.gitbooks.io/building-web-apps-with-go/content/)
 * [Darker Corners of Go](https://rytisbiel.com/2021/03/06/darker-corners-of-go/) - Rytis Bieliunas