code: func ValidateSignature(signature string, payload, secretToken []byte) error {
  	messageMAC, hashFunc, err := messageMAC(signature)
  	if err != nil {
  		return err
  	}
  	if !checkMAC(payload, messageMAC, secretToken, hashFunc) {
  		return errors.New("payload signature check failed")
  	}
  	return nil
  }
docs: // ValidateSignature validates the signature for the given payload.
  // signature is the GitHub hash signature delivered in the X-Hub-Signature header.
  // payload is the JSON payload sent by GitHub Webhooks.
  // secretToken is the GitHub Webhook secret token.
  //
  // GitHub API docs: https://developer.github.com/webhooks/securing/#validating-payloads-from-github