fix request head timeout (#2611)

actix-http/examples/h2spec.rs

@@ -0,0 +1,25 @@
+use std::{convert::Infallible, io};
+
+use actix_http::{HttpService, Request, Response, StatusCode};
+use actix_server::Server;
+use once_cell::sync::Lazy;
+
+static STR: Lazy<String> = Lazy::new(|| "HELLO WORLD ".repeat(100));
+
+#[actix_rt::main]
+async fn main() -> io::Result<()> {
+    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));
+
+    Server::build()
+        .bind("h2spec", ("127.0.0.1", 8080), || {
+            HttpService::build()
+                .h2(|_: Request| async move {
+                    let mut res = Response::build(StatusCode::OK);
+                    Ok::<_, Infallible>(res.body(&**STR))
+                })
+                .tcp()
+        })?
+        .workers(4)
+        .run()
+        .await
+}