fix httpauth extraction error handling in middleware (#128)

actix-web-httpauth/examples/middleware-closure.rs

@@ -2,7 +2,7 @@ use actix_web::{middleware, web, App, HttpServer};
 
 use actix_web_httpauth::middleware::HttpAuthentication;
 
-#[actix_rt::main]
+#[actix_web::main]
 async fn main() -> std::io::Result<()> {
     HttpServer::new(|| {
         let auth = HttpAuthentication::basic(|req, _credentials| async { Ok(req) });