Add GeeksforGeeks Golang course (#5807)

courses/free-courses-en.md

@@ -337,6 +337,7 @@
 * [Go Tutorial](http://www.tutorialspoint.com/go/index.htm)
 * [Golang \| Gin HTTP Framework](https://www.youtube.com/playlist?list=PL3eAkoh7fypr8zrkiygiY1e9osoqjoV9w) - Pragmatic Reviews
 * [Golang in under an hour](https://www.youtube.com/watch?v=N0fIANJkwic) - Eli Goldberg
+* [Golang Tutorial - Learn Go Programming Language](https://www.geeksforgeeks.org/golang-tutorial-learn-go-programming-language/) - GeeksforGeeks
 * [Gophercises: Free Coding Exercises for Budding Gophers](https://gophercises.com) - Jon Calhoun (email address *required*)
 * [Learn Go Programming - Golang Tutorial for Beginners](https://www.youtube.com/watch?v=YS4e4q9oBaU) - FreeCodeCamp