test.go

package main

import "fmt"

type Something interface {
	DoA()
	DoB()
}

type Person struct {
}

func (p *Person) DoA() {
	fmt.Println("Person A")
}
func (p *Person) DoB() {
	fmt.Println("Person B")
}

type SuperPerson struct {
	Something
}

func (p *SuperPerson) DoA() {
	fmt.Println("SuperPerson A")
}

func main() {
	p := &Person{}
	sp := &SuperPerson{p}
	test(sp)
}

func test(obj Something) {
	obj.DoA()
	obj.DoB()
}