add example program from discuss

examples/discuss1.ml

@@ -0,0 +1,27 @@
+(** Example from https://discuss.ocaml.org/t/confused-about-moonpool-cancellation/15381 *)
+
+let ( let@ ) = ( @@ )
+
+let () =
+  let@ () = Trace_tef.with_setup () in
+  let@ _ = Moonpool_fib.main in
+
+  (* let@ runner = Moonpool.Ws_pool.with_ () in *)
+  let@ runner = Moonpool.Background_thread.with_ () in
+
+  (* Pretend this is some long-running read loop *)
+  for i = 1 to 10 do
+    Printf.printf "MAIN LOOP %d\n%!" i;
+    Moonpool_fib.check_if_cancelled ();
+    let _ : _ Moonpool_fib.t =
+      Moonpool_fib.spawn ~on:runner ~protect:false (fun () ->
+          Printf.printf "RUN FIBER %d\n%!" i;
+          Moonpool_fib.check_if_cancelled ();
+          Format.printf "FIBER %d NOT CANCELLED YET@." i;
+          failwith "BOOM")
+    in
+    Moonpool_fib.yield ();
+    (* Thread.delay 0.2; *)
+    (* Thread.delay 0.0001; *)
+    ()
+  done

examples/dune

@@ -0,0 +1,12 @@
+(executables
+ (names discuss1)
+ (enabled_if
+  (>= %{ocaml_version} 5.0))
+ ;(package moonpool)
+ (libraries
+  moonpool
+  moonpool.fib
+  trace
+  trace-tef
+  ;tracy-client.trace
+  ))