How to change session timeout duration for angular portal?

WebDesigner uses the session timeout specified in web.config, for example

    <sessionState mode="InProc" stateConnectionString="tcpip=127.0.0.1:42424" sqlConnectionString="data source=127.0.0.1;Trusted_Connection=yes" cookieless="false" timeout="60"/>

but what about angular portal? how to customize the duration?