update examples to v4 (#258)

examples/async-handlers/Cargo.toml

@@ -4,6 +4,6 @@ version = "2.0.0"
 edition = "2018"
 
 [dependencies]
-actix-web = "3"
+actix-web = "4"
 futures = "0.3.1"
 bytes = "0.5"

examples/async-handlers/src/stream.rs

@@ -14,7 +14,7 @@ async fn stream() -> HttpResponse {
 #[actix_web::main]
 async fn main() -> std::io::Result<()> {
     HttpServer::new(|| App::new().service(stream))
-        .bind("127.0.0.1:8080")?
+        .bind(("127.0.0.1", 8080))?
         .run()
         .await
 }