webpack: that myloader run this.callback is undefined in myloader.js

Do you want to request a feature or report a bug? I think it’s bug

What is the current behavior? I want to develop a loader , but I can’t invoke callback of loader API .

If the current behavior is a bug, please provide the steps to reproduce. this is myloader.js

const loaderUtils = require("loader-utils");

/*
  1、返回一个字符串
  2、source 是一个对象
*/
module.exports = function(source) {
  console.log('-------------------------hLoader-start----------------------------->');
  console.log('source', source);
  // console.log('this-------------------------->',this); // this of node
  console.log("callback------------->",this.callback); // undefined
  console.log('-------------------------hLoader-end----------------------------->');
  return "sdfjslkdjfljsdlfjlsdfj";
};

What is the expected behavior?

If this is a feature request, what is motivation or use case for changing the behavior?

Please mention other relevant information such as the browser version, Node.js version, webpack version and Operating System.