在ASP.NET API控制器操作中更新cookie的到期日期

Struggling to find an answer to this. I set a cookie which essentially allows me to track a visitors shopping cart. Setting the cookie is fine but I can't find a way of updating the expiry date, so that each time the user does something cart related it updates to 90 days in the future. My code below. This is the AddToCart API method in question.Struggling to find an answer to this. I set a c