以阮一峰的例子來看：var fs = require('fs');var readFile = function (fileName) {  return new Promise(function (resolve, reject) {    fs.readFile(fileName, function(error, data) {      if (error) reject(error);      resolve(data);    });  });};var asyncReadFile = async function () {  var f1 = await readFile('/etc/fstab');  var f2 = await readFile('/etc/shells');  console.log(f1.toString());  console.log(f2.toString());};在這個里面，如果我想每次把readFile里面的error打印出來，請問這個該怎么在async函數里面處理呢？