Using DSN Connection and knowing windows username

Hi,

i am using windows server 2012 and connecting from Access FE to Postgresql
using DSN connection.

When i am using "select current_user;" in postgresql i have always user
"postgres" because it is my default user for database.

How to know in postgresql which specific windows user is using database?
How to solve this?

I tried to use method from here:

https://www.cafe-encounter.net/p2034/postgres-using-integrated-security-on-windows-on-localhost

but this is only to avoid inputing password by specific windows server
user.
(and this is not working also).

Please help,
Best,
Jacek