--- a/util/async.lua	Sat Jul 07 21:55:18 2018 +0200
+++ b/util/async.lua	Sun Jul 08 00:37:01 2018 +0200
@@ -1,5 +1,6 @@
 local logger = require "util.logger";
 local log = logger.init("util.async");
+local timer = require "util.timer";
 local new_id = require "util.id".short;
 
 local function checkthread()
@@ -245,9 +246,16 @@
 	return pcall(checkthread);
 end
 
+local function sleep(s)
+	local wait, done = waiter();
+	timer.add_task(s, done);
+	wait();
+end
+
 return {
 	ready = ready;
 	waiter = waiter;
 	guarder = guarder;
 	runner = runner;
+	sleep = sleep;
 };