local unpack = unpack or table.unpack;

 local function async_to_sync(async_func, callback_pos)

     return function(...)

         local _co = coroutine.running() or error ('this function must be run in coroutine')

         local rets

         local waiting = false

         local function cb_func(...)

             if waiting then

                 assert(coroutine.resume(_co, ...))

             else

                 rets = {...}

             end

         end

         local params = {...}

         table.insert(params, callback_pos or (#params + ), cb_func)

         async_func(unpack(params))

         if rets == nil then

             waiting = true

             rets = {coroutine.yield()}

         end

         return unpack(rets)

     end

 end

 -- 异步协程

 local gameobject = CS.UnityEngine.GameObject('XLua_Coroutine_Runner');

 CS.UnityEngine.Object.DontDestroyOnLoad(gameobject);

 local csCoroutineRunner = gameobject:AddComponent(typeof(CS.XLuaCoroutineRunner));

 local function AsyncYieldReturn(toYield, cb)

     csCoroutineRunner:YieldAndCallback(toYield, cb)

 end

 local yieldReturn = async_to_sync(AsyncYieldReturn);

 -- 协程

 local co = coroutine.create(function()

     local url = CS.Common.LoadHelp.GetAssetBundleStreamingUrl("xxx.json");

     local www = CS.UnityEngine.WWW(url);

     yieldReturn(www);

     local text = www.text;

     print(text);

 end);

 coroutine.resume(co);