renderToString(App, { awaiter } );

class App extends Component {
   constructor(owner, args) {
      super(owner, args);
      // sync awaiter registration;
      this.onComponentLoaded = this.args.awaiter.register("componentLoaded");
      import('components/my-component').then((result) => {
         this.componentToRender = result.default;
         setTimeout(() => {
              // async awaiter  resolution
              this.onComponentLoaded.resolve();
          });
      })
   }
}

class App extends Component {
   @tracked data;
   constructor(owner, args) {
      super(owner, args);
      // sync awaiter registration;
      this.onDataLoaded = this.args.awaiter.register("dataLoaded");
      fetch('api/users').then(result => result.toJSON()).then((data) => {
                  this.data = data;
                  setTimeout(() => {
                        this.onDataLoaded.resolve();
                   });
       });
   }
}