code: func insecureRegisterClient(params RegisterParams) (*Client, error) {
  	tlsConfig := utils.TLSConfig(params.CipherSuites)
  
  	cert, err := readCA(params)
  	if err != nil && !trace.IsNotFound(err) {
  		return nil, trace.Wrap(err)
  	}
  
  	// If no CA was found, then create a insecure connection to the Auth Server,
  	// otherwise use the CA on disk to validate the Auth Server.
  	if trace.IsNotFound(err) {
  		tlsConfig.InsecureSkipVerify = true
  
  		log.Warnf("Joining cluster without validating the identity of the Auth " +
  			"Server. This may open you up to a Man-In-The-Middle (MITM) attack if an " +
  			"attacker can gain privileged network access. To remedy this, use the CA pin " +
  			"value provided when join token was generated to validate the identity of " +
  			"the Auth Server.")
  	} else {
  		certPool := x509.NewCertPool()
  		certPool.AddCert(cert)
  		tlsConfig.RootCAs = certPool
  
  		log.Infof("Joining remote cluster %v, validating connection with certificate on disk.", cert.Subject.CommonName)
  	}
  
  	client, err := NewTLSClient(ClientConfig{Addrs: params.Servers, TLS: tlsConfig})
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  
  	return client, nil
  }
docs: // insecureRegisterClient attempts to connects to the Auth Server using the
  // CA on disk. If no CA is found on disk, Teleport will not verify the Auth
  // Server it is connecting to.