sample: simulate timeout to demonstrate caching

sample/20-cache/src/app.controller.ts

@@ -5,7 +5,10 @@ import { Controller, Get, UseInterceptors } from '@nestjs/common';
 @UseInterceptors(CacheInterceptor)
 export class AppController {
   @Get()
-  findAll() {
+  async findAll() {
+    // For demonstration purposes, we will simulate a delay
+    // to show that the cache is working as expected.
+    await new Promise(resolve => setTimeout(resolve, 3000));
     return [{ id: 1, name: 'Nest' }];
   }
 }