local co_time_tbl = {}

 setmetatable(co_time_tbl, { __len = function(o)

     local count =

     for k, v in pairs(o) do

         count = count +

     end

     return count

 end

 })

 local function isWindows()

     return package.config:sub(, ) == "\\"

 end

 local function sleep(n)

     if isWindows() then

         if n >  then

             os.execute("ping -n " .. tonumber(n + ) .. " localhost > NUL")

         end

     else

         os.execute("sleep " .. tonumber(n))

     end

 end

 local function Update(deltaTime)

     -- main loop

 end

 local function updateCoroutine()

     local iTime = os.time()

     for kco, vTime in pairs(co_time_tbl) do

         if iTime >= vTime then

             if coroutine.status(kco) == "suspended" or coroutine.status(kco) == "normal" then

                 coroutine.resume(kco)

             elseif coroutine.status(kco) == "dead" then

                 co_time_tbl[kco] = nil

             end

         end

     end

 end

 function coroutine.waitforSeconds(second)

     assert(type(second) == "number" or second <= )

     local iEndTime = os.time() + second

     local co = coroutine.running()

     if co then

         co_time_tbl[co] = iEndTime

         return coroutine.yield()

     end

 end

 local function main()

     local co1 = coroutine.wrap(function()

         coroutine.waitforSeconds()

         print("after 5 seconds")

     end)

     local co2 = coroutine.wrap(function()

         coroutine.waitforSeconds()

         print("after 4 seconds")

     end)

     local co3 = coroutine.wrap(function()

         coroutine.waitforSeconds()

         print("after 3 seconds")

     end)

     local count =

     local co4 = coroutine.wrap(function()

         while (true) do

             coroutine.waitforSeconds()

             count = count +

             print("coroutine num: " .. #co_time_tbl .. " | second count:" .. count)

         end

     end)

     co1()

     co2()

     co3()

     co4()

     while true do

         sleep(0.033)

         Update()

         updateCoroutine()

     end

 end

 main()