如何在Angular 8的应用初始化中初始化几个root提供的服务？

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { HttpClientModule } from '@angular/common/http';

import { AppComponent } from './app.component';
import { DataService } from './services/data.service';
import { AuthService } from './services/auth.service';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, HttpClientModule],
  providers: [DataService, AuthService], // 在这里初始化服务
  bootstrap: [AppComponent]
})
export class AppModule { }

import { Injectable } from '@angular/core';

@Injectable()
export class DataService {
  constructor() {
    // 在构造函数中进行服务的初始化
    console.log('DataService initialized');
  }
}

@Injectable()
export class AuthService {
  constructor() {
    // 在构造函数中进行服务的初始化
    console.log('AuthService initialized');
  }
}