Retain `client_address` on Postgres connection when using Private IP

### Question

We're currently rewriting a number of our Golang services to use `cloudsqlconn` and overall things are working great.

However one thing that we've spotted is that there's no `client_address` reported on the connections within Postgres, even if we're using the instance private IP to connect.
However if we connect using `psql` from the same pod using the same details then the `client_address` _is_ recorded.

So is there a specific reason why the `client_address` isn't being reported when connecting via `cloudsqlconn` using the private IP?

### Code

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### Additional Details

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