App Initializer

app.initializer.ts

export function appInitializer(/* authenticationService: AuthenticationService */) {
    return () => new Promise(resolve => {
        console.log("app initialize");
    });
}

app.module.ts

providers: [
    { provide: APP_INITIALIZER, useFactory: appInitializer, multi: true/*, deps: [AuthenticationService]*/ }
],

becareful about the deps and injection parts...