interface1.go

package main

import (
  "fmt"
)

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

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

func main() {
    c := Cat{}
    fmt.Println("Cat says:", c.Say())
    d := Dog{}
    fmt.Println("Dog says:", d.Say())
}