code: func clientSideVerifier(tlsCfg *tls.Config, rawCerts [][]byte) error {
  	_, err := verifyChain(tlsCfg, rawCerts, true)
  	return err
  }
docs: // clientSideVerifier is a verifierFunc that performs verification of certificates
  // on the client end of the connection. For now it is just basic TLS
  // verification since the identity check needs additional state and becomes
  // clunky to customize the callback for every outgoing request. That is done
  // within Service.Dial for now.