tokenService vindo null Erro 500

package br.com.alura.forum.config.security;

import java.util.Date;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.security.core.Authentication;
import org.springframework.stereotype.Service;

import br.com.alura.forum.modelo.Usuario;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

@Service
public class TokenService {

    @Value("${forum.jwt.expiration}")
    private String expiration;

    @Value("${forum.jwt.secret}")
       private String secret;

    public String gerarToken(Authentication auth) {

        Usuario user = (Usuario) auth.getPrincipal();
        Date hoje = new Date();

        Date dataExp = new Date(hoje.getTime() + Long.parseLong(expiration));



        return Jwts.builder().setIssuer("API do forum Alura")
                .setSubject(user.getId().toString())
                .setIssuedAt(hoje)
                .setExpiration(dataExp)
                .signWith(SignatureAlgorithm.HS256, secret)
                .compact();
    }

}

package br.com.alura.forum.controller;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import br.com.alura.forum.config.security.TokenService;
import br.com.alura.forum.controller.formDto.LoginForm;

@RestController
@RequestMapping("/auth")
public class AutenticacaoController {

    @Autowired 
    private AuthenticationManager authManager;

    private TokenService tokenService;

    @PostMapping
    public ResponseEntity<?> autenticar(@RequestBody @Valid LoginForm form){

        UsernamePasswordAuthenticationToken dadosLogin = form.converter();

        try {
            Authentication auth = authManager.authenticate(dadosLogin);
            String token = tokenService.gerarToken(auth);
            System.out.println(token);
            return ResponseEntity.ok().build();
        } catch (AuthenticationException e) {
            return ResponseEntity.badRequest().build();
        }



    }
}