Novice:
https://tour.golang.org/methods/1
https://tour.golang.org/methods/2
https://tour.golang.org/methods/3
https://tour.golang.org/methods/9
https://tour.golang.org/methods/10
https://tour.golang.org/methods/11
https://tour.golang.org/methods/12
https://tour.golang.org/methods/13
https://tour.golang.org/methods/14
https://golang.org/doc/effective_go#interfaces
Intermediate:
https://tour.golang.org/methods/16
https://golang.org/doc/effective_go#type_switch
Advanced:
https://tour.golang.org/methods/13
Expert:
https://tour.golang.org/methods/15
https://tour.golang.org/methods/21