code: func AESDecryptWithCBC(cryptStr, key []byte, iv []byte) ([]byte, error) {
  	cb, err := aes.NewCipher(key)
  	if err != nil {
  		return nil, errors.Trace(err)
  	}
  	mode := cipher.NewCBCDecrypter(cb, iv)
  	return aesDecrypt(cryptStr, mode)
  }
docs: // AESDecryptWithCBC decrypts data using AES with CBC mode.