the-way-to-go_ZH_CN/eBook/examples/chapter_10/methodset1.go

// methodset1.go
package main

import (
	"fmt"
)

type List []int
func (l List) Len() int { return len(l) }
func (l *List) Append(val int) { *l = append(*l, val) }

func main() {
	  // A bare value
        var lst List
        lst.Append(1)
        fmt.Printf("%v (len: %d)\n", lst, lst.Len()) // [1] (len: 1)

        // A pointer value
        plst := new(List)
        plst.Append(2)
        fmt.Printf("%v (len: %d)\n", plst, lst.Len()) // &[2] (len: 1)
}