How to ignore idle timeout from AWS ELB in the browser

I have an application where a user can upload a PDF using angular-file-upload.js

My elastic load balancer is configured to have an idle timeout of 10 seconds and other parts of the application depend on keeping this parameter.

The issue is if the file upload takes longer than 10 seconds the user receives a 504 Gateway Timeout in the browser and an error message. However, the file still reaches the server after some time.

How can I ignore or not show the user this 504 Gateway Timeout that comes from the ELB?

Source: AngularJS