Map asynchronous query data after render interface

  node.js, question
exports.index = function(req, res, next) {
 var result = {};
 var getData = [
 bracket
 shcema: Car,
 example: 'car_list'
 },
 bracket
 shcema: Brand,
 example: 'brands'
 bracket
 bracket
 async.map(getData, function(item, callback){
 //assign a value to result
 // ……
 }, function(err,r){
 //Final callback rendering is invalid
 res.render('index', result);
 })
 
 };

For example, the render interface is invalid in the callback, and the value of result cannot be obtained under the map function.

function(item, callback){
 //Did you forget to call callbacks in this function?
 bracket

Callback must be called, otherwise the following function(err, r) will never be executed.