ADD: implements exit function

@@ -13,6 +13,15 @@ func main() {
 		fmt.Print("input: ")
 		sc.Scan()
 		input = sc.Text()
+
+		exit(input)
+
 		fmt.Printf("output: %s\n", input)
 	}
+}
+
+func exit(input string) {
+	if input == "exit" {
+		os.Exit(0)
+	}
 }
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