Support functions with parameters

hello/hello.go

@@ -6,9 +6,19 @@ const SIX = 6
 func main() {
 	println("Hello world from Go!")
 	println("The answer is:", calculateAnswer())
+	println("5 ** 2 =", square(5))
+	println("3 + 12 =", add(3, 12))
 }
 
 func calculateAnswer() int {
 	seven := 7
 	return SIX * seven
 }
+
+func square(n int) int {
+	return n * n
+}
+
+func add(a, b int) int {
+	return a + b
+}