小程序使用async函数后开启es6转码后报错

WAService.js:3 thirdScriptError
regeneratorRuntime is not defined;at pages/dome1/dome1 page test function
ReferenceError: regeneratorRuntime is not defined
    at http://127.0.0.1:9973/appservice/pages/dome1/dome1.js:47:50
    at e.test (http://127.0.0.1:9973/appservice/pages/dome1/dome1.js:85:6)
    at e.<anonymous> (http://127.0.0.1:9973/appservice/__dev__/WAService.js:15:4257)
    at e.a (http://127.0.0.1:9973/appservice/__dev__/WAService.js:14:31107)
    at K (http://127.0.0.1:9973/appservice/__dev__/WAService.js:14:25691)
    at Function.<anonymous> (http://127.0.0.1:9973/appservice/__dev__/WAService.js:14:27280)
    at http://127.0.0.1:9973/appservice/__dev__/WAService.js:15:647
    at http://127.0.0.1:9973/appservice/__dev__/WAService.js:6:8176
    at e.(anonymous function) (http://127.0.0.1:9973/appservice/__dev__/WAService.js:3:31751)
    at d (http://127.0.0.1:9973/appservice/appservice:1100:8304)

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   let start = async function () {

     try{

       that.write("start");      

       await sleep(3000)

       that.write("end");

     }catch(err){

       console.log(err)

     }

   }

   start();