Can I restrict users to access my application?

My application have google authentication oAuth API. I want to give access to few users to my application with google account.

@lavanya Please check our documentation regarding access control - https://docs.appsmith.com/core-concepts/access-control.

Not by sharing the application. I want to restrict while login to the application.

By restricting, do you mean to parts of the application/pages? If yes, then we are still working on this epic and can be tracked here - [Epic] Granular Access Control | RBAC · Issue #3317 · appsmithorg/appsmith · GitHub

If your database supports user roles and privileges, then this can be implemented to a certain degree by controlling visibility as shown in this demo video below where users with different roles and privileges see different tabs after logging in - How To Build An Inventory Management Tool With HarperDB - YouTube

Please feel free to reach out in case of any queries

In a organisation i shared the aplication to few members. Can i use this users/members in coding.

Appsmith has a user object from which you can access the email id of the user who is currently logged in.
For eg: {{appsmith.user.email}}

This would be ok if you only want to check for and restrict access to a a few known users.

Link to doc - https://docs.appsmith.com/framework-reference/appsmith#user