Hello world controller

WebAPI/Controllers/HelloWorldController.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+
+namespace WebAPI.Controllers
+{
+    [Route("api/[controller]")]
+    [ApiController]
+    public class HelloWorldController : ControllerBase
+    {
+        [HttpGet]
+        public async Task<string> HelloWorld()
+        {
+            await Task.Delay(5000);
+            return "Hello world!";
+        }
+    }
+}