diff --git a/rust/asyncfnstore/Cargo.lock b/rust/asyncfnstore/Cargo.lock
new file mode 100644
index 0000000..487d9dd
--- /dev/null
+++ b/rust/asyncfnstore/Cargo.lock
@@ -0,0 +1,339 @@
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+# It is not intended for manual editing.
+version = 3
+
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diff --git a/rust/asyncfnstore/Cargo.toml b/rust/asyncfnstore/Cargo.toml
new file mode 100644
index 0000000..d318017
--- /dev/null
+++ b/rust/asyncfnstore/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "asyncfnstore"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+tokio = { version = "1.43.0", features = ["full"] }
diff --git a/rust/asyncfnstore/src/main.rs b/rust/asyncfnstore/src/main.rs
new file mode 100644
index 0000000..e16ade3
--- /dev/null
+++ b/rust/asyncfnstore/src/main.rs
@@ -0,0 +1,55 @@
+//use futures::future::BoxFuture;
+use std::future::Future;
+use std::pin::Pin;
+
+
+struct Data {
+    num: usize
+}
+
+async fn bar(data: &Data) -> usize {
+    data.num + 666
+}
+
+async fn lorem(data: &Data) -> usize {
+    data.num + 777
+}
+
+type BoxFuture<'a, T> = Box<dyn Future<Output = T> + 'a>;
+type CallbackDyn = dyn for<'a> Fn(&'a Data) -> BoxFuture<'a, usize>;
+
+struct Foo {
+    one: Box<CallbackDyn>,
+    data: Data,
+}
+
+impl Foo {
+    fn set<F>(&mut self, f: F) 
+        where F: for<'a> Fn(&'a Data) -> BoxFuture<'a, usize> + 'static {
+        self.one = Box::new(f);
+    }
+
+    async fn process(mut self) {
+        let func = &self.one;
+        println!("Result: {}", Box::into_pin(func(&self.data)).await);
+    }
+}
+
+#[tokio::main]
+async fn main() {    
+    let mut foo = Foo {
+        one: Box::new(|i| Box::new(bar(i))),
+        data: Data{num: 3},
+    };
+    //let mut foo = Foo::new(bar);
+    let offset = 5;
+    foo.set(move |d| {
+        Box::new(async move {
+            let i = lorem(d).await;
+            i + offset
+        })
+    });
+
+    foo.process().await;
+    
+}
diff --git a/rust/tokiorace/src/main.rs b/rust/tokiorace/src/main.rs
index f6ac397..7e78e32 100644
--- a/rust/tokiorace/src/main.rs
+++ b/rust/tokiorace/src/main.rs
@@ -1,18 +1,18 @@
 use tokio::{
     task,
-    time::{Duration, sleep},
+    time::{Instant, Duration, sleep},
     sync::{oneshot,
            mpsc::{Receiver, Sender, channel}
     }
 };
-use std::collections::{VecDeque, HashMap};
+use std::collections::{HashMap};
 use anyhow::Result;
 use anyhow::{bail, Context};
-use tracing::{info, debug, instrument, Level};
-use tracing_subscriber::{fmt, Registry, EnvFilter};
+use tracing::{info, debug, instrument};
+use tracing_subscriber::{fmt, EnvFilter};
 use tracing_subscriber::prelude::*;
-use tracing_subscriber::fmt::format::FmtSpan;
-use tokio::runtime::Handle;
+use std::future::Future;
+
 
 struct Service {
     t: Transport,
@@ -24,10 +24,15 @@ struct Event {
     in_reply_to: Option<usize>,
 }
 
-type CB = dyn (FnMut(Event, &mut Transport) -> Result<()>) + Send;
+//type CB<'a> = Box<dyn Fn(Event, &'a mut Transport) -> Box<dyn Future<Output = Result<()>>>>;
+
+//type CB<'a> = dyn Fn(Event, &mut Transport) -> BoxFuture<'a, Result<()>>;
+
+type BoxFuture<'a, T> = Box<dyn Future<Output = T> + 'a>;
+type CallbackDyn = dyn for<'a> Fn(Event, &'a mut Transport) -> BoxFuture<'a, Result<()>>;
 
 enum Handler {
-    Callback(Box<CB>),
+    Callback(Box<CallbackDyn>),
     Channel(oneshot::Sender<Event>)
 }
 
@@ -35,7 +40,7 @@ struct Transport {
     msg_id: usize,
     outbox: Sender<Event>,
     inbox: Receiver<Option<Event>>,
-    callbacks: HashMap<usize, Handler>,
+    callbacks: HashMap<usize, (Handler, Instant)>,
 }
 
 
@@ -55,28 +60,45 @@ impl Transport {
     #[instrument(level="debug",skip(self),ret)]
     fn close(&mut self) -> Result<()> {
         self.inbox.close();
-        Ok(())
+        let i = Instant::now();
+        self.callbacks.retain(|_, (_, t)| *t >= i);
+        if self.callbacks.is_empty() {
+            Ok(())
+        } else {
+            bail!("some callbacks failed to launch.")
+        }
     }
 
     #[instrument(level="debug",skip(self),ret)]
-    async fn send(&mut self, e: Event) -> Result<()> {
+    async fn send(&self, e: Event) -> Result<()> {
         self.outbox.send(e).await.context("unable to send message")
     }
+
     #[instrument(level="debug",skip(self),ret)]
     async fn rpc(&mut self, e: Event) -> Result<Event> {
-        let id = e.id;
-        self.send(e).await?;
-        let (tx, rx) = oneshot::channel();
-        self.callbacks.insert(id, Handler::Channel(tx));
+        let rx = self.rpc_chan(e).await?;
         let resp = rx.await?;
         Ok(resp)
     }
 
-    async fn rpc_callback<C: FnMut(Event, &mut Transport) -> Result<()> + Send + Sized + 'static>(&mut self, e: Event, cb: C) -> Result<()> {
-        self.callbacks.insert(e.id, Handler::Callback(Box::new(cb)));
+    #[instrument(level="debug",skip(self),ret)]
+    async fn rpc_chan(&mut self, e: Event) -> Result<oneshot::Receiver<Event>> {
+        let id = e.id;
+        self.send(e).await?;
+        let (tx, rx) = oneshot::channel();
+        self.callbacks.insert(id, (Handler::Channel(tx), Instant::now() + Duration::from_millis(1000)));
+        Ok(rx)
+    }
+
+    async fn rpc_callback<C>(&mut self, e: Event, cb: C) -> Result<()>
+        where
+        C: for<'a> Fn(Event, &'a mut Transport) -> BoxFuture<'a, Result<()>> + 'static
+    {
+        self.callbacks.insert(e.id, (Handler::Callback(Box::new(cb)), (Instant::now() + Duration::from_millis(1000))));
         self.send(e).await
     }
 
+    /// #Cancellation safety: This method is **not** cancellation safe, because it deals with callbacks
     #[instrument(level="debug",skip(self),ret)]
     async fn recv(&mut self) -> Result<Option<Event>> {
         loop {
@@ -89,16 +111,25 @@ impl Transport {
             let Some(original) = nxt.in_reply_to else {
                 return Ok(Some(nxt));
             };
-            match self.callbacks.remove(&nxt.id) {
+            let sp = match self.callbacks.remove(&original) {
                 None => {
                     return Ok(Some(nxt));
                 },
-                Some(Handler::Callback(mut cb)) => {
-                    cb(nxt, self)?;
+                Some((h, t)) => {
+                    if t < Instant::now() {
+                        continue;
+                    }
+                    h
+                }
+            };
+            match sp {
+                Handler::Callback(cb) => {
+                    let f = Box::into_pin(cb(nxt, self));
+                    f.await?;
                 },
-                Some(Handler::Channel(c)) => {
+                Handler::Channel(c) => {
                     if let Err(e) = c.send(nxt) {
-                        bail!("could not send event to callback")
+                        bail!("could not send event to callback {e:?}")
                     }
                 }
             }
@@ -106,6 +137,17 @@ impl Transport {
     }
 }
 
+macro_rules! callback {
+    (|$e:ident, $svc:ident| $blk:block) => {
+        |$e, $svc| {
+            Box::new(async move {
+                $blk
+            })
+        }
+    }
+
+}
+
 impl Service {
     #[instrument(level="debug", skip(self),ret)]
     async fn process(&mut self, event: Event) -> Result<()>{
@@ -117,16 +159,9 @@ impl Service {
     #[instrument(level="debug", skip(self),ret)]
     async fn process_nonblocking(&mut self, event: Event) -> Result<()>{
         let resp = self.t.rpc_callback(Event{id: event.id, in_reply_to: None},
-                                       |e, svc| {
-                                           let handle = Handle::current();
-                                           task::block_in_place(move || {
-                                               handle.block_on(
-                                                   async move {
-                                                       svc.send(Event{id: 199, in_reply_to: Some(e.id)}).await
-                                                   })
-                                           })
-                                       }
-                                       ).await?;
+                                       callback!(|e, svc| {
+                                               svc.send(Event{id: 199, in_reply_to: Some(e.id)}).await
+                                           })).await?;
         debug!("{:?}", &resp);
         Ok(())
     }
@@ -136,7 +171,7 @@ impl Service {
         while let Some(e) = self.t.recv().await? {
             self.process_nonblocking(e).await?;
         }
-        Ok::<(), anyhow::Error>(())
+        self.t.close()
     }
 
 }
@@ -148,9 +183,11 @@ async fn main() -> Result<()> {
     .with(EnvFilter::from_default_env())
     .init();
 
+    info!("Starting example server");
+
     let (t, tx, mut rx) = Transport::new();
 
-    let mut serv = Service{t};
+    let serv = Service{t};
 
     let tx1 = tx.clone();
     let s = tokio::spawn(async move {
@@ -162,28 +199,29 @@ async fn main() -> Result<()> {
     });
     debug!("Serving");
     let r = tokio::spawn(async move {
-        for i in 0..5 {
+        for i in 0..2 {
             let Some(msg) = rx.recv().await else {
                 break;
             };
             if msg.in_reply_to.is_some() {
                 continue;
             }
-            sleep(Duration::from_millis(1000)).await;
-            let reply = Event{id: 99, in_reply_to: Some(msg.id)};
-            debug!("Sending reply: {:?}", &reply);
-            tx.send(Some(reply)).await.context("could not send reply")?;
+            sleep(Duration::from_millis(200)).await;
+            if i < 0 {
+                let reply = Event{id: 99, in_reply_to: Some(msg.id)};
+                debug!("Sending reply: {:?}", &reply);
+                tx.send(Some(reply)).await.context("could not send reply")?;
+            } else {
+                println!("DONE WITH REPLIES");
+            }
         }
-        println!("DONE WITH REPLIES");
-        sleep(Duration::from_millis(5000)).await;
-        println!("REALLY DONE WITH REPLIES");
+        sleep(Duration::from_millis(100)).await;
         tx.send(None).await.context("could not send closing message")?;
         Ok(())
     });
     serv.serve().await?;
 
-    debug!("Served");
-    //serv.close();
+    info!("Served");
     s.await.context("error joining")??;
     r.await.context("error joining send")?
 }