Implement a Golang function that accepts a string as input and returns its reverse without using any built-in functions or libraries.
PLAINFORMAT
package main

import (
	"fmt"
)

// reverseString takes a string as input and returns its reverse
func reverseString(s string) string {
	runes := []rune(s)
	length := len(runes)
	for i := 0; i < length/2; i++ {
		runes[i], runes[length-1-i] = runes[length-1-i], runes[i]
	}
	return string(runes)
}

func main() {
	input := "Hello, World!"
	reversed := reverseString(input)
	fmt.Println("Original:", input)
	fmt.Println("Reversed:", reversed)
}