Поговорим
за жизнь 
производительность

import 'library';

import * as library from 'library';

import library from library;

import {method} from library;

const toastrFactory = () => import('toastr').then(p => p.default);

type LazyToastr = ReturnType<typeof toastrFactory>;
const TOASTR = new InjectionToken<LazyToastr>('Lazily loaded toastr', {
  providedIn: 'root',
  factory: toastrFactory
});