SharePoint Provided Hosted App: getting error-Request timed out. System.Web.HttpException: Request timed out

I have created a SharePoint Provided-hosted app. trying to importing in excel to SharePoint list, I run this app after some time getting the message "Request time out".

I have tried few ways like adding below tag in web.config file

<httpRuntime  executionTimeout="3600" />

and tried this one also. context.RequestTimeout = 1000 * 60 * 3;

but still getting same error "Request time out."

Server Error in '/' Application. Request timed out.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Request timed out.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[HttpException (0x80004005): Request timed out.]