Async series is not calling properly - node.js

Question

I have 3 function has to call in series one after the other. but first function is exeucting and in between second and third are executing.
var tasklist=[api_hit,delay,mysql_check];
if(task_list.length>0){
async.series(
tasklist,
function(err, response) {
console.log(err);
console.log(response);
results.data=response;
results.message="Completed";
console.log(results);
}
);
}
Internal functions:
function api_hit(callback){
console.log("Inside api");
var ele=task_list[0];
var apidata=[];
var msg={'data':[]};
apiinfo.forEach((item,key)=>{
if(item.Method_name==ele.Parameters){
//Here checking random Int value
if(item.Value=="{{$randomInt}}"){
item.Value = generate(25);
}
apidata.push(item);
}
});
var data=[];
data['api']=apidata;
apiModel.validateAPI(data,function(res){
console.log("result api");
msg.data=res;
msg.case='api_hit';
callback(msg);
});
}
function delay(callback){
console.log("Inside delay");
var msg={'data':[]};
global_vars.sleep(1000);
msg.data='success';
msg.case='task';
console.log("after delay");
callback(msg);
}
function mysql_check(callback){
console.log("inside mysql");
var ele=task_list[2];
var dbdata=[];
var msg={'data':[]};
dbchecks.forEach((item,key)=>{
if(item.query_id==ele.Parameters){
console.log(item.query+" ::: "+ele.Parameters);
dbdata.push(item);
}
});
data['dbdata']=dbdata;
apiModel.checkmysql(data,function(err,res){
if(err) throw err;
console.log("inside mysql res");
msg.data=res;
msg.case='task2';
callback(msg);
});
}
My intention is to call these function after completing of others and all the results has to process in a single variable. but in api_hit method when it is executing another function inside of it then delay()(second function of async) is executing. how to stop this and make it in sequence. thanks in advance.

Answer 1

The first argument to the callback function is the error, pass null in case of success.
'use strict'
const async = require('async')
function api_hit(callback) {
setTimeout(() => {
console.log('Completed api_hit')
callback(null, 'api_hit')
}, 1000)
}
function delay(callback) {
setTimeout(() => {
console.log('Completed delay')
callback(null, 'delay')
}, 100)
}
function mysql_check(callback) {
setTimeout(() => {
console.log('Completed mysql_check')
callback(null, 'mysql_check')
}, 500)
}
var tasklist = [api_hit, delay, mysql_check];
if (tasklist.length > 0) {
async.series(
tasklist,
function (err, response) {
console.log(err);
console.log(response);
}
);
}
Doc link: https://caolan.github.io/async/docs.html#series