Access map element (that does not exist)

• What happens when we access an element that does not exist?
• Go returns 0.
• So we can't know if the field exists and its value is 0 or if it does not exist at all.

package main

import "fmt"

func main() {
	grades := make(map[string]int)

	grades["Mary"] = 99
	grades["Joe"] = 0
	fmt.Println(grades["Mary"])
	fmt.Println(grades["Joe"])
	fmt.Println(grades["Jane"])

}

99
0
0