node.js, can't get response from callback when execute function on a for loop -

i want make simulation log in web application multiple users in node.js
have function login(), , execute in loop simulate log in many users.
when maxthreads > 5, sometimes don't receive response callback request in function login() code is:

var request = require("request"); var cheerio = require("cheerio");   function login(i){ request({   uri: "http://example.com/sign_in",   method: "post",   timeout: 1000,   followallredirects: true,   form: {     email: "mail@example.com",     password: "password"   }       }, function (error, response, body) {     var $ = cheerio.load(body);     var title = $("title");     console.log(title.html()+ "-" + );              }); }  var maxthreads = 10 for(i=0; i<maxthreads; i++){   login(i) } 

example output:

null-5 null-6 null-7 null-8 null-9 exapmle title-0 exapmle title-1 exapmle title-3 exapmle title-2 exapmle title-4 

my problem: whan have more threads - have more null responses

you use async module instead of loop. way you'd have more control on control flow.