Ionic 4 TokenInterceptor

With Ionic 4, what is the suggested way to use a token interceptor?
I thought there was something new and built in with v4 but am not finding it back.

I am currently trying to use the following but am getting a cyclic dependency error.

import { Injectable, Injector } from '@angular/core';
import {
} from '@angular/common/http';
import { AuthService } from './auth.service';
import { Observable } from 'rxjs';
export class TokenInterceptor implements HttpInterceptor {
  constructor(private injector: Injector) {}
  intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const authService = this.injector.get(AuthService);
    request = request.clone({
      setHeaders: {
        Authorization: 'Bearer ' +authService.getToken()
    return next.handle(request);


providers: [
    AuthService, {
      provide: HTTP_INTERCEPTORS,
      useClass: TokenInterceptor,
      multi: true
    }, ...

Or should I be using Angular 6 JWT Interceptor?

Is there something conflicting in AuthService?

Nothing obvious.
But is this even remotely how we should be using interceptors/auth-guards now with v4?
With the angular routing I thought there was a different recommended approach?