golang Aes

package models

import (
    "bytes"
    "crypto/aes"
    "crypto/cipher"
    "errors"                                                                                                                                                                 
)

const (
    ivDefValue = "0102030405060708"
)

func AesEncrypt(plaintext []byte, key []byte) ([]byte, error) {
    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, errors.New("invalid decrypt key")
    }   
    blockSize := block.BlockSize()
    plaintext = PKCS5Padding(plaintext, blockSize)
    iv := []byte(ivDefValue)
    blockMode := cipher.NewCBCEncrypter(block, iv) 

    ciphertext := make([]byte, len(plaintext))
    blockMode.CryptBlocks(ciphertext, plaintext)

    return ciphertext, nil 
}

func AesDecrypt(ciphertext []byte, key []byte) ([]byte, error) {

    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, errors.New("invalid decrypt key")
    }   

    blockSize := block.BlockSize()

    if len(ciphertext) < blockSize {
        return nil, errors.New("ciphertext too short")
    }   

    iv := []byte(ivDefValue)
    if len(ciphertext)%blockSize != 0 { 
        return nil, errors.New("ciphertext is not a multiple of the block size")
    }   

    blockModel := cipher.NewCBCDecrypter(block, iv)

    plaintext := make([]byte, len(ciphertext))
    blockModel.CryptBlocks(plaintext, ciphertext)
    plaintext = PKCS5UnPadding(plaintext)

    return plaintext, nil
}

func PKCS5Padding(src []byte, blockSize int) []byte {
    padding := blockSize - len(src)%blockSize
    padtext := bytes.Repeat([]byte{byte(padding)}, padding)
    return append(src, padtext...)
}

func PKCS5UnPadding(src []byte) []byte {
    length := len(src)
    unpadding := int(src[length-1])
    if length - unpadding <= 0 {
        return src
    }
    return src[:(length - unpadding)]
}