code: func AESDecryptWithCFB(cryptStr, key []byte, iv []byte) ([]byte, error) {
  	cb, err := aes.NewCipher(key)
  	if err != nil {
  		return nil, errors.Trace(err)
  	}
  	cfb := cipher.NewCFBDecrypter(cb, []byte(iv))
  	dst := make([]byte, len(cryptStr))
  	cfb.XORKeyStream(dst, cryptStr)
  	return dst, nil
  }
docs: // AESDecryptWithCFB decrypts data using AES with CFB mode.