MEAN client-server connection timeout for downloading PDF - node.js

Question

I am using MEAN Stack for our project. To generate pdf using pdfmake,
scenario goes like, At first have images from local server so every thing works fine. For scalibility have to move images to AWS and data from other server.
Now processs is like, first download images from aws then make buffer, convert it to base64 and give it to pdfmake. Now issue arises for client-server connection.
client makes http request for pdf, server process it but it takes too much time to download image from aws, so client connection breaks mean while
server processing the request and send response back but no one is there to listen.
/** client **/
function logicTriplogs() {
$rootScope.isLoading = true;
AssignsService.logicTriplogs({
driverId: vm.driver
}, {
_ids: vm.selectedTrips,
scheduleTime: vm.scheduleTime,
companyImage: vm.companyImage
},
function(response) {
console.log(response);
$rootScope.isLoading = false;
var Name = response.pdfName;
var data = response.content;
SaveFile.downloadURI(Name, data);
console.log('PDF Name:', Name);
},
function(err) {
console.log(err);
vm.error = err.data.message;
$rootScope.isLoading = false;
});
}
/** Server **/
getAssignedTripQuery(query, type)
.exec(function(err, assigns) {
if (err) {
console.log('Manifest');
return res.status(400).send({
message: errorHandler.getErrorMessage(err)
});
}
if (assigns.length) {
logicMan(req.body, user, driver, assigns, function(docDefinition) {
var pdfName = `${moment_tz.tz(startDay, req.user.timeZone).format('MM-DD-YYYY')}.pdf`;
config.pdfBuffer(docDefinition, function(err, pdfDoc) {
console.log('EROROR PDF: ', err);
if (err) {
console.log('pdfmake function call error');
return res.status(400).send({
message: 'Error while generate pdf'
});
}
console.log('PDF Name:', pdfName);
return res.json({
message: 'Generated Susscessfuly',
pdfName: pdfName,
content: pdfDoc
});
});
});
} else {
return res.status(400).send({
message: 'Some thing went wrong. Please try later.'
});
}
});