study tutorial for Go
- https://go.dev/doc/
- https://go.dev/doc/effective_go
- https://go.dev/play/
- https://go.dev/blog/
- https://gobyexample.com/
- https://kubernetes.io/docs/tutorials/kubernetes-basics/
- https://www.youtube.com/watch?v=yWCSYgZSOhg
a function whose name starts with a capital letter can be called by a function not in the same package.