Introduction to generics from “Learn Go wil tests”: A nice tutorial that takes a step approach to teach generics starting from duplicating code for types, then to interface{}, and finally to generics. And you can run it all in the go2go playground.
https://quii.gitbook.io/learn-go-with-tests/meta/intro-to-generics
https://quii.gitbook.io/learn-go-with-tests/meta/intro-to-generics