interface2.go

package main

import(
  "fmt"
  "reflect"
)

type Cat struct{}
func (c Cat) Say() string{return "meow"}

type Dog struct{}
func (d Dog) Say() string{return "woof"}

type Horse struct{}
func (h Horse) Say() string{return "neigh"}

func main(){
  c:=Cat{}
  d:=Dog{}
  
  //initialize them into an array
  animals:=[]Sayer{c,d}
  
  //append horse into array
  animals=append(animals,Horse{})
  
  for _,a:= range animals{
    MakeTalk(a)
  }
}

type Sayer interface{
  Say() string
}

func MakeTalk(s Sayer){
  fmt.Println(reflect.TypeOf(s).Name(), "says:", s.Say())
}