contact_map.go

package main

import "fmt"

func main() {
	contacts := map[string]string{}
	contacts["John"] = "02-12345678"
	contacts["Mary"] = "02-12345678"

	if _, ok := contacts["Mary"]; ok {
		fmt.Println("Mary is in the contacts")
	}

	if phoneNumber, _ := contacts["Mary"]; phoneNumber == "02-12345678" {
		fmt.Println("correct phone number")
	}
	fmt.Printf("items %+v\n", contacts)
}