README.md: fix HttpClientFactory example (#28)

* README.md: fix HttpClientFactory example

* Update README.md

README.md

@@ -67,10 +67,10 @@ public void ConfigureServices(IServiceCollection services)
 public class ValuesController : Controller
 {
     [HttpGet("{id}")]
-    public async Task<string> Get(int id, [FromServices] IHttpClientFactory httpClientFactory)
+    public Task<string> Get(int id, [FromServices] IHttpClientFactory httpClientFactory)
     {
         var httpClient = httpClientFactory.CreateClient("sw-tracing");
-        return await httpClient.GetStringAsync("http://api.xxx.com/values");
+        return httpClient.GetStringAsync("http://api.xxx.com/values");
     }
 }
 ```