How to handle timescale when using admob?

I am using google admob rewarded interstitial ads and before showing/closing the ad timescale is set to 0 but as soon as I click on close ad button it sets the timescale back to 1 itself.

ADMob automatically sets the timescale to 0 when showing an ad, so that the game doesn’t run in the background. If you want the timescale to be continued with value 0 after you close the ad, you can implement the AdClose Handle:

this.rewardedAd.OnAdClosed += HandleRewardedAdClosed;

and in the method you set your timescale to 0

public void HandleRewardedAdClosed(object sender, EventArgs args)
    {
        Time.timeScale = 0;
    }