let btns= document.getElementsByTagName('btn');
    let cancel = null;
    btns[0].onclick = function (){
      if(cancel !== null){
        cancel();
        //检测上一次的请求是否完成，如果未完成则取消请求
      }
      axios(
        {
          method: 'GET',
          url: 'http://localhost:9000/posts',
          cancelToken : new axios.CanselToken(function (c){
            cancel = c;
          })
        }
      ).then(response=>{
        console.log(response);
        cancel = null;//初始化Cancel
      })
    }