Fix a Host example: https://github.com/kataras/iris/issues/1451

Host.md

@@ -136,7 +136,8 @@ There may be times that you want something very special to listen on, which is n
 // the responsibility of starting up a listener is up to you with this way,
 // for the sake of simplicity we will use the
 // ListenAndServe function of the `net/http` package.
-app.Run(iris.Raw(&http.Server{Addr:":8080"}).ListenAndServe)
+srv := &http.Server{Addr:":8080"}
+app.Run(iris.Raw(srv.ListenAndServe))
 ```
 
 ## Host configurators