Here is an "advanced" example of using an auth guard.

canActivate(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable<boolean | UrlTree> | Promise<boolean | UrlTree> | boolean | UrlTree {
    let newState: State = INITSTATE;

    return this.authService.session()
      .pipe(
        switchMap(resp => {
          if (resp.ok) {
            return this.userService.getUser();
          }
          return throwError("Forbidden");
        }),
        catchError(error => {
          if (error.status == 500) {
            this.authService.startLogout();
          } else if (error.status == 401) {
            this.authService.startLogin();
          }
          return throwError(error);
        }), ........
				// more code here
				
				
				// auth service can look something like this
				
  session(): Observable<HttpResponse<string>>{
    return this.http.get<string>("/api/auth/session", {observe: 'response'})
  }


  startLogout(): void {
    window.open("/api/auth/sso-logout", '_self');
  }

  startLogin(): void {
    let next = location.pathname;
    window.open("/api/auth/login" + next, '_self');
  }
				
				// on the backend side for example:
				
	@GET
  @PermitAll
  @Path("/session")
  public Response session(@Context SecurityContext ctx) {
    if (ctx.getUserPrincipal() == null) {
      return Response.status(Response.Status.UNAUTHORIZED).build();
    }
    return Response.status(Response.Status.OK).build();
  }
				

This code ist taken from an active project an needs to be adjusted to your needs :)