title: RouterModule.forRoot() called twice
body: <p>I'm trying to implement lazyloading into my angular 5 app, but i get error: </p>
  
  <p>Uncaught (in promise): Error: RouterModule.forRoot() called twice. Lazy loaded modules should use RouterModule.forChild() instead.</p>
  
  <p>There my routing modules: 
  <strong>app-routing.module.ts</strong></p>
  
  <pre><code>import { NgModule } from "@angular/core";
  import { RouterModule, Routes } from "@angular/router";
  
  // import Commponents for router
  
  import { MainPageComponent } from "../pages/main/main-page.component";
  import { AboutCompanyPageComponent } from "../pages/about-company/about-company-page.component";
  import { MediaPageComponent } from "../pages/media/media-page.component";
  import { ChangePasswordComponent } from "../components/change-password/change-password.component";
  import { ConfirmOrderComponent } from "../pages/confirm-order/confirm-order.component";
  import { NoConnectionComponent } from "../pages/no-connection/no-connection.component";
  import { NotFoundComponent } from "../pages/not-found/not-found.component";
  import { SearchComponent } from "../pages/search/search.component";
  import { PaymentComponent } from "../pages/payment/payment.component";
  import { WorkersGeoLocationComponent } from "../pages/workers-geo-location/workers-geo-location.component";
  import { AdminProfileModule } from "../modules/admin-profile/admin-profile.module";
  
  const routes: Routes = [
      {
          path: "",
          component: MainPageComponent
      },
      {
          path: "about",
          component: AboutCompanyPageComponent
      },
      {
          path: "payment",
          component: PaymentComponent
      },
      {
          path: "media",
          component: MediaPageComponent
      }, {
          path: "profile/workersGeoLocation",
          component: WorkersGeoLocationComponent
      },
      {
          path: "admin",
          loadChildren: '../modules/admin-profile/admin-profile.module#AdminProfileModule'
          // loadChildren: () =&gt; AdminProfileModule
      },
      {
          path: "password/recovery",
          component: ChangePasswordComponent
      },
      {
          path: "search",
          component: SearchComponent
      },
      {
          path: "confirm",
          component: ConfirmOrderComponent
      },
      {
          path: "no-connection",
          component: NoConnectionComponent
      },
      {
          path: "**",
          component: NotFoundComponent
      }
  ];
  
  @NgModule({
      imports: [
          RouterModule.forRoot(routes)
      ],
      exports: [
          RouterModule
      ]
  })
  export class AppRoutingModule {
  }
  </code></pre>
  
  <p>There I use forRoot() method for RouterModule. </p>
  
  <p>In my second module, which should be lazy loaded I use forChild() method, </p>
  
  <p>There some code: </p>
  
  <pre><code>import { NgModule } from '@angular/core';
  import { RouterModule, Routes } from "@angular/router";
  import { OrdersTabComponent } from "../../components/tabs/orders-tab/orders-tab.component";
  
  const routes: Routes = [
      {
          path: '',
          component: OrdersTabComponent
      }
  ];
  
  @NgModule({
      imports: [
          RouterModule.forChild(routes)
      ],
      exports: [
          RouterModule
      ]
  })
  
  export class AdminRoutingModule { }
  </code></pre>
  
  <p>And as u can see there are only two modules with separate methods for RouterModule and I can't understand where is mistake. </p>
  
  <p>Can anybody help me with it? </p>