Maintain individual variables for GO

So I am trying to implement a notifications package in go for multiple front ends. The design is whenever a user reads a notification on one device it must erase the unread notifications from other devices. For which I maintain a global time stamp which is updated whenever a user clicks on notification on any of the tabs. So how do I implement this feature. Because there will be multiple users how do I make sure a user is not updating the timestamp of another user.

Thanks!