You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rot13.go
    path of file: ./repos/al-go-rithms/cryptography/rot13_cipher/go
    
    the code of the file until where you have to start completion: package main

// Rot13 apply rot13 algorithm given a plaintext and returns ciphertext
func Rot13(plaintext string) (ciphertext string) {
	rotation := 13

	for _, char := range plaintext {

		if char >= rune('A') && char <= rune('Z') {
			decrementRotation := int(char)+rotation > int(rune('Z'))
			if decrementRotation {
				ciphertext += string(int(char) - rotation)
			} else {
				ciphertext += string(int(char) + rotation)
			}
		} else if char >= rune('a') && char <= rune('z') {
			decrementRotation := int(char)+rotation > int(rune('z'))
    
func Rot13(plaintext string) (ciphertext string) {
	rotation := 13

	for _, char := range plaintext {

		if char >= rune('A') && char <= rune('Z') {
			decrementRotation := int(char)+rotation > int(rune('Z'))
			if decrementRotation {
				ciphertext += string(int(char) - rotation)
			} else {
				ciphertext += string(int(char) + rotation)
			}
		} else if char >= rune('a') && char <= rune('z') {
			decrementRotation := int(char)+rotation > int(rune('z'))
			if decrementRotation {
				ciphertext += string(int(char) - rotation)
			} else {
				ciphertext += string(int(char) + rotation)
			}
		} else {
			ciphertext += " "
		}

	}

	return
}