app.module.ts

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

import { UserService } from './user.service';
import { LogService } from './log.service';

@NgModule({
  imports: [LogService, UserService]
})
class AppModule {
  constructor(logService: LogService, userService: UserService) {
    logService.initialize().then(() => userService.initialize());
  }
}