Add serve function and remove Server re-export (#1868)

examples/cors/src/main.rs

@@ -40,10 +40,8 @@ async fn main() {
 
 async fn serve(app: Router, port: u16) {
     let addr = SocketAddr::from(([127, 0, 0, 1], port));
-    axum::Server::bind(&addr)
-        .serve(app.into_make_service())
-        .await
-        .unwrap();
+    let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
+    axum::serve(listener, app).await.unwrap();
 }
 
 async fn html() -> impl IntoResponse {