Challenge 2 — Solution

Task: Using the same stock map, use the comma-ok idiom to check for
"grapes" (which doesn't exist) and "apples" (which does), printing
an appropriate message for each case.

package main

import "fmt"

func main() {
	stock := map[string]int{"apples": 15, "bananas": 5, "oranges": 8}

	quantity, exists := stock["grapes"]
	if exists {
		fmt.Println("Grapes in stock:", quantity)
	} else {
		fmt.Println("No grapes in stock.")
	}

	quantity, exists = stock["apples"]
	if exists {
		fmt.Println("Apples in stock:", quantity)
	} else {
		fmt.Println("No apples in stock.")
	}
}


Expected output:

No grapes in stock.
Apples in stock: 15

Notes:
- stock["grapes"] alone would have silently returned 0 with no way
  to tell that "grapes" was never actually added — the comma-ok form
  is what makes "doesn't exist" distinguishable from "exists with a
  value of 0".
- quantity and exists are reused (with =, not :=) for the second
  lookup since both variables already exist from the first.
- This same pattern is used constantly in real Go code any time it
  genuinely matters whether a map key was set at all.