code: func (tr *Transport) TLSClientAuthClientConfig(host string) (*tls.Config, error) {
  	cert, err := tr.getCertificate()
  	if err != nil {
  		return nil, err
  	}
  
  	return &tls.Config{
  		Certificates: []tls.Certificate{cert},
  		RootCAs:      tr.TrustStore.Pool(),
  		ServerName:   host,
  		CipherSuites: core.CipherSuites,
  		MinVersion:   tls.VersionTLS12,
  		ClientAuth:   tls.RequireAndVerifyClientCert,
  	}, nil
  }
docs: // TLSClientAuthClientConfig returns a new client authentication TLS
  // configuration that can be used for a client using client auth
  // connecting to the named host.