var async = require("async");
var request = require('superagent'); 

var urls = [
  "https://www.npmjs.com/package/async",
  "https://caolan.github.io/async/",
  "https://www.baidu.com/",
  "https://www.tslang.cn/",
  "http://www.jtthink.com/"
]

async.mapLimit(urls, 2, async function(value, key) {
    const response = await fetchs(value)
    return response
}, (err, results) => {
    if (err) throw err
    // results is now an array of the response bodies
    console.log(results)
})

async function fetchs(url){
  return new Promise(function(resolve,reject){
    request
    .get(url)
    .end((err, res) => {
      resolve(res.text)
    });
  })
}