Not able to get rid of "No 'Access-Control-Allow-Origin' header is present on the requested resource"

I am stuck on this… please help on what can be the issue.
i am trying to access using aws api gateway

serverless.yml is as below.

And
index.js is

const serverless = require(‘serverless-http’);
const bodyParser = require(‘body-parser’);
const express = require(‘express’);
const app = express();

var AWS = require(‘aws-sdk’);

var dynamodb = new AWS.DynamoDB();
var lambda = new AWS.Lambda();
var s3 = new AWS.S3();
var jwt = require(‘jsonwebtoken’);
var uniqid = require(‘uniqid’);

var JWT_PARAM={
TableName:‘JWTSECRET’,
Key:{
‘Secret’:{S:‘secret1’}
},
ProjectionExpression:‘SecretValue’
};
var JWT_SECRET = null;

app.use(bodyParser.json({ strict: false }));

app.use(function(request, response, next) {
response.header(“Access-Control-Allow-Origin”, “*”);
response.header(“Access-Control-Allow-Headers”, “Origin, X-Requested-With, Content-Type, Accept”);
next();
});

app.post(’/uploadImage’, function (req, res) {

if(JWT_SECRET){
	//some code to be done
	res.set({
		   "Access-Control-Allow-Origin" : "*",
			});
	res.status(200).send('some text');
}
else{
	dynamodb.getItem(JWT_PARAM, (err, data)=>{
		if(err){
			res.set({
		   "Access-Control-Allow-Origin" : "*",
			});
			res.status(200).send('some text');
		else{
			JWT_SECRET=data.Item.SecretValue.S;
			var token=req.headers.authorization;
			var user= jwt.verify(token,JWT_SECRET);
			var fileName = req.files.file.name;
			var key= uniqid(fileName+'.');
			var uploadParams = {Bucket: 'web.document.images',
								Key	  :key,
								Body  :req.files.file.data };
			s3.upload (uploadParams,  (err, data)=> {
				if (data) 
				{
					res.set({
					   "Access-Control-Allow-Origin" : "*",
						});
					res.status(200).send('some text');			
				}
				else{
					res.set({
					   "Access-Control-Allow-Origin" : "*",
						});
					res.status(200).send('some text');
				} 
			}); 
		}		
	});
}

});

module.exports.handler = serverless(app);