Retrieve username from current data connection

Hi,

I have a use case where I'm writing a custom M function that requires the username from the current data connector's connection. For example, I am connected to Teradata database using teradata database credentials, and I want to retrieve the username that was used while authenticating to Teradata database in my custom M function.

I'm defining this M function in custom data connector. I tried using Extension.CurrentCredential()[Username] to get the username from credentials but got the following error:

Expression.Error: We can only perform this operation while using a custom data connector.

Is there a way to do this?

Thanks,

Namrata