Server implementation of the Language Service

app.server.module.ts

@NgModule({
  imports: [
    // The AppServerModule should import your AppModule followed
    // by the ServerModule from @angular/platform-server.
    AppModule,
    ServerModule,
    ServerTransferStateModule,
    NoopAnimationsModule
  ],
  providers: [
    ...
    { provide: LanguageService, useClass: ServerLanguageService }
  ],
  // Since the bootstrapped component is not inherited from your
  // imported AppModule, it needs to be repeated here.
  bootstrap: [AppComponent]
})
export class AppServerModule {}