Adds spawn with function

ntex-rt/src/arbiter.rs

@@ -154,6 +154,27 @@ impl Arbiter {
             .try_send(ArbiterCommand::Execute(Box::pin(future)));
     }
 
+    /// Send a function to the Arbiter's thread and spawns it's resulting future.
+    /// This can be used to spawn non-send futures on the arbiter thread.
+    pub fn spawn_with<F, R, O>(&self, f: F) -> impl Future<Output = Result<O, oneshot::RecvError>> + Send + 'static
+    where
+        F: FnOnce() -> R + Send + 'static,
+        R: Future<Output = O> + 'static,
+        O: Send + 'static
+    {
+        let (tx, rx) = oneshot::channel();
+        let _ = self
+            .sender
+            .try_send(ArbiterCommand::ExecuteFn(Box::new(move || {
+                let fut = f();
+                let fut = Box::pin(async {
+                    let _ = tx.send(fut.await);
+                });
+                crate::spawn(fut);
+            })));
+        rx
+    }
+
     /// Send a function to the Arbiter's thread. This function will be executed asynchronously.
     /// A future is created, and when resolved will contain the result of the function sent
     /// to the Arbiters thread.