Lua asynchronous and synchronous sleeping

sleep.lua

function sleep(time, func, ...)
	local now = os.time()
	local thread = coroutine.create(func)
	repeat until (os.time() - now > time)
	coroutine.resume(thread, ...)
end

function asleep(time, func, ...)
	coroutine.wrap(function()
		local now = os.time()
		local thread = coroutine.create(func)
		repeat until (os.time() - now > time)
		coroutine.resume(thread, ...)
	end)()
end

When I attempt a similar implementation, "repeat until" simply freezes the entire program, not only the coroutine.