hello and goodbye functions

src/main.rs

@@ -1,4 +1,13 @@
 /// This is the best implementation of this program to ever exist.
 fn main() {
+    print_hello();
+    print_goodbye();
+}
+
+fn print_hello() {
     println!("Hello, world!");
 }
+
+fn print_goodbye() {
+    println!("Goodbye, world!");
+}