Update 'fairings' example for async.

examples/fairings/src/main.rs

@@ -35,7 +35,10 @@ impl Fairing for Counter {
         }
     }
 
-    fn on_response(&self, request: &Request<'_>, response: &mut Response<'_>) {
+    fn on_response<'a, 'r>(&'a self, request: &'a Request<'r>, response: &'a mut Response<'r>)
+        -> std::pin::Pin<Box<dyn std::future::Future<Output=()> + Send + 'a>>
+    {
+        Box::pin(async move {
             if response.status() != Status::NotFound {
                 return
             }
@@ -49,6 +52,7 @@ impl Fairing for Counter {
                 response.set_header(ContentType::Plain);
                 response.set_sized_body(Cursor::new(body));
             }
+        })
     }
 }
 
@@ -82,10 +86,12 @@ fn rocket() -> rocket::Rocket {
             }
         }))
         .attach(AdHoc::on_response("Response Rewriter", |req, res| {
+            Box::pin(async move {
                 if req.uri().path() == "/" {
                     println!("    => Rewriting response body.");
                     res.set_sized_body(Cursor::new("Hello, fairings!"));
                 }
+            })
         }))
 }