code: func CertAtuh(ctx *neptulon.ReqCtx) error {
  	if _, ok := ctx.Session.GetOk("userid"); ok {
  		return ctx.Next()
  	}
  
  	// if provided, client certificate is verified by the TLS listener so the peerCerts list in the connection is trusted
  	// connState, _ := ctx.Conn.ConnectionState()
  	// certs := connState.PeerCertificates
  	// if len(certs) == 0 {
  	// 	log.Println("Invalid client-certificate authentication attempt:", ctx.Conn.RemoteAddr())
  	// 	ctx.Conn.Close()
  	// 	return nil
  	// }
  	//
  	// userID := certs[0].Subject.CommonName
  	// ctx.Session.Set("userid", userID)
  	// log.Printf("Client authenticated. TLS/IP: %v, User ID: %v, Conn ID: %v\n", ctx.Conn.RemoteAddr(), userID, ctx.Conn.ID)
  	return ctx.Next()
  }
docs: // CertAtuh is TLS client-certificate authentication.
  // If successful, certificate common name will stored with the key "userid" in session.
  // If unsuccessful, connection will be closed right away.