Angular注入配置服务时config未定义问题求助

这是此前相关问题的跟进内容，已调试许久，虽未解决但有一些发现，寻求帮助。

完整项目结构 #

app-config.json（/src/assets/） #

{
  "apiUrl": "localhost:8080"
}

app-config.service.ts（/src/app/） #

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

@Injectable({
  providedIn: 'root'
})
export class AppConfigService {

  private appConfig: any;

  constructor (private injector: Injector) { }

  loadAppConfig() {
    let http = this.injector.get(HttpClient);

    return http.get('/assets/app-config.json')
      .toPromise()
      .then(data => {
        this.appConfig = data;
      })
  }

  get config() {
    return this.appConfig;
  }

}

app.module.ts（/src/app/） #

import {APP_INITIALIZER, NgModule} from '@angular/core';
import {HttpClientModule} from '@angular/common/http';
import {AppConfigService} from './app-config.service';
import {CometdService} from './cometd/cometd.service';

const appInitializerFn = (appConfig: AppConfigService) => {
  return () => {
    return appConfig.loadAppConfig();
  }
};

@NgModule({
...
  providers: [HttpClientModule,
    AppConfigService,
    {
      provide: APP_INITIALIZER,
      useFactory: appInitializerFn,
      multi: true,
      deps: [AppConfigService]
    }]
})

export class AppModule {
  constructor(cometdService: CometdService) {}
}

cometd.service.ts（/src/app/cometd/） #

import {Injectable, OnDestroy} from '@angular/core';
import {Store} from '@ngrx/store';
import * as fromRoot from '../reducers';
import {AppConfigService} from '../app-config.service';

export interface CometDExtended extends cometlib.CometD {
  websocketEnabled: boolean;
}

@Injectable({
  providedIn: 'root'
})
export class CometdService implements OnDestroy {

  protected cometd: CometDExtended = new cometlib.CometD() as CometDExtended;

  private subscriptions: cometlib.SubscriptionHandle[] = [];

  constructor(private environment: AppConfigService, private store: Store<fromRoot.State>) {
    let config = environment.config;
    let apiUrl = environment.config.apiUrl;
    
    this.cometd.configure('http://localhost:8080/cometd');
    this.startConnection();
  }
...
}

已发现的现象 #

• 该问题并非仅出现在CometdService，多个服务均受影响；
• AppConfigService的loadAppConfig()能正确获取到{ "apiUrl": "localhost:8080" }数据；
• 注入的AppConfigService实例已定义，为Object类型；
• environment.config为undefined，读取environment.config.apiUrl时触发错误：TypeError: Cannot read properties of undefined (reading 'apiUrl')。

内容的提问来源于stack exchange，提问作者podehi