Added a link to the Golang by Example website (EbookFoundation#9229)

* Added a link to the Golang by Example website

* Remove trailing slash

books/free-programming-books-langs.md

@@ -822,6 +822,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [Go Succinctly](https://www.syncfusion.com/succinctly-free-ebooks/go-succinctly) - Mark Lewin (PDF, EPUB, Kindle)
 * [Go Tutorial](http://www.tutorialspoint.com/go/) - Tutorials Point (HTML, PDF)
 * [Go Web Development Succinctly](https://www.syncfusion.com/succinctly-free-ebooks/go-web-development) - Mark Lewin (PDF, EPUB, Kindle)
+* [Golang by Example](https://golangbyexample.com) 
 * [How To Code in Go](https://www.digitalocean.com/community/books/how-to-code-in-go-ebook) - Mark Bates, Cory Lanou, Timothy J. Raymond (PDF, EPUB)
 * [Learn Go in Y minutes](https://learnxinyminutes.com/docs/go/)
 * [Learn Go with Tests](https://quii.gitbook.io/learn-go-with-tests/)