JWT 사용 시 auth 변수 null

auth 변수는 null로 나오고 SecurityContextHolder에서 불러오면 출력이 잘 됩니다..
auth는 왜 null로 나오는걸까요?ㅠㅠ

-------------- controller --------------------------------
@GetMapping("/my-page/jwt")
@ResponseBody
String mypageJWT(Authentication auth){
    System.out.println(SecurityContextHolder.getContext().getAuthentication());
    if (auth == null) auth = SecurityContextHolder.getContext().getAuthentication();

    CustomUser user = (CustomUser) auth.getPrincipal();
    System.out.println(user);
    System.out.println(user.getDisplayName());
    System.out.println(user.getAuthorities());

return "mypage.html";
}

------------ filter ----------------------

@Override
    protected void doFilterInternal(
      HttpServletRequest request, 
      HttpServletResponse response, 
      FilterChain filterChain
    ) throws ServletException, IOException {

        Cookie[] cookies = request.getCookies();
        if (cookies == null){
            filterChain.doFilter(request,response);
            return;
        }

        var jwtCookie = "";
        for (int i = 0; i < cookies.length; i++){
            if (cookies[i].getName().equals("jwt")){
                jwtCookie = cookies[i].getValue();
            }
        }

        Claims claim;
        try {
            claim = JwtUtil.extractToken(jwtCookie);
        } catch (Exception e) {
            filterChain.doFilter(request, response);
            return;
        }

        CustomUser customUser = new CustomUser(claim.get("username").toString()
                , ""
                , Arrays.stream(claim.get("authorities").toString().split(",")).map(x -> new SimpleGrantedAuthority(x)).toList() //authorities
                );
        customUser.setDisplayName(claim.get("displayName").toString());

        UsernamePasswordAuthenticationToken authToken = new UsernamePasswordAuthenticationToken(customUser, "" );
        authToken.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
        SecurityContextHolder.getContext().setAuthentication(authToken);
//        System.out.println(SecurityContextHolder.getContext().getAuthentication());

        filterChain.doFilter(request, response);
    }