What is wrong with this Angular service code using HttpClient?

What is wrong with this Angular service code using HttpClient?

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class ApiService {
  constructor(private http: HttpClient) {}

  fetchData() {
    return this.http.get('https://api.example.com/items').subscribe(data => {
      console.log(data);
    });
  }
}