How to set timeout for sling servlet in AEM6.4

Hi Team,

We are using sling servlet with POST method in our AEM6.4 application. We are receiving "504 Gateway timeout" response, due to long processing (we are connecting to external service from sling servlet) time. Could you please let me know, if there is way to fix it like changing timeout for sling servlet.

<form action="/slingservlet" method="POST">

        <button class="coral-Link coral-Button">Post Request</button>

    </form>

Thanks

Seran