--- a/teal-src/plugins/mod_cron.tl	Sun May 08 18:06:41 2022 +0200
+++ b/teal-src/plugins/mod_cron.tl	Sun May 08 15:21:35 2022 +0200
@@ -88,7 +88,7 @@
 	task:save(started_at);
 end
 
-local task_runner = async.runner(run_task);
+local task_runner : async.runner_t<task_spec> = async.runner(run_task);
 module:add_timer(1, function() : integer
 	module:log("info", "Running periodic tasks");
 	local delay = 3600;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/teal-src/util/async.d.tl	Sun May 08 15:21:35 2022 +0200
@@ -0,0 +1,42 @@
+local record lib
+	ready : function () : boolean
+	waiter : function (num : integer, allow_many : boolean) : function (), function ()
+	guarder : function () : function (id : function ()) : function () | nil
+	record runner_t<T>
+		func : function (T)
+		thread : thread
+		enum state_e
+			-- from Lua manual
+			"running"
+			"suspended"
+			"normal"
+			"dead"
+
+			-- from util.async
+			"ready"
+			"error"
+		end
+		state : state_e
+		notified_state : state_e
+		queue : { T }
+		type watcher_t = function (runner_t<T>, ... : any)
+		type watchers_t = { state_e : watcher_t }
+		data : any
+		id : string
+
+		run : function (runner_t<T>, T) : boolean, state_e, integer
+		enqueue : function (runner_t<T>, T) : runner_t<T>
+		log : function (runner_t<T>, string, string, ... : any)
+		onready : function (runner_t<T>, function) : runner_t<T>
+		onready : function (runner_t<T>, function) : runner_t<T>
+		onwaiting : function (runner_t<T>, function) : runner_t<T>
+		onerror : function (runner_t<T>, function) : runner_t<T>
+	end
+	runner : function <T>(function (T), runner_t.watchers_t, any) : runner_t<T>
+	wait_for : function (any) : any, any
+	sleep : function (t:number)
+
+	-- set_nexttick = function(new_next_tick) next_tick = new_next_tick; end;
+	-- set_schedule_function = function (new_schedule_function) schedule_task = new_schedule_function; end;
+end
+return lib