fix request head timeout (#2611)

actix-http/src/notify_on_drop.rs

@@ -0,0 +1,49 @@
+/// Test Module for checking the drop state of certain async tasks that are spawned
+/// with `actix_rt::spawn`
+///
+/// The target task must explicitly generate `NotifyOnDrop` when spawn the task
+use std::cell::RefCell;
+
+thread_local! {
+    static NOTIFY_DROPPED: RefCell<Option<bool>> = RefCell::new(None);
+}
+
+/// Check if the spawned task is dropped.
+///
+/// # Panics
+/// Panics when there was no `NotifyOnDrop` instance on current thread.
+pub(crate) fn is_dropped() -> bool {
+    NOTIFY_DROPPED.with(|bool| {
+        bool.borrow()
+            .expect("No NotifyOnDrop existed on current thread")
+    })
+}
+
+pub(crate) struct NotifyOnDrop;
+
+impl NotifyOnDrop {
+    /// # Panics
+    /// Panics hen construct multiple instances on any given thread.
+    pub(crate) fn new() -> Self {
+        NOTIFY_DROPPED.with(|bool| {
+            let mut bool = bool.borrow_mut();
+            if bool.is_some() {
+                panic!("NotifyOnDrop existed on current thread");
+            } else {
+                *bool = Some(false);
+            }
+        });
+
+        NotifyOnDrop
+    }
+}
+
+impl Drop for NotifyOnDrop {
+    fn drop(&mut self) {
+        NOTIFY_DROPPED.with(|bool| {
+            if let Some(b) = bool.borrow_mut().as_mut() {
+                *b = true;
+            }
+        });
+    }
+}