Abstracting a method to an interface

interface2.go

package main
 
import "fmt"
 
type Greeter interface {
	Greet()
}

type Man struct {
	language string
	
	// other factors to decide if the girl would like you (for fun)
	name, nationality, build, eye_color string
	age, height uint8
	// you could be in debt, so we can't rule out negative values
	income int64
	// this is to remind her you are available
	married	bool
}
 
func (m Man) Greet() {
	switch m.language {
	case "British" : fmt.Println("Good morning, dear")
	case "American": fmt.Println("Mornin' there")
	case "Japanese": fmt.Println("Ohayou Gozaimasu")
	case "Thai"    : fmt.Println("Arunsawad Krub")
	default        : fmt.Println("Good morning")
	}
}
 
func main() {
	jay := new(Man)	
	james := new(Man)
	john := new(Man)
	
	jy := Greeter(jay)
	jm := Greeter(james)
	jn := Greeter(john)
	
	jay.language = "Japanese"
	james.language = "Thai"
	john.language = "British"
	
	jy.Greet()	// print "Ohayou Gozaimasu"
	jm.Greet()	// print "Arunsawad Krub"
	jn.Greet()    // print "Good morning, dear"
}