Is it possible to use peer authentication to connect to Postgres in a Kubernetes sidecar running in the same container?

I am using postgres_exporter as a sidecar in k8s to collect Postgres metrics in a Postgres pod. I would like to use peer authentication (i.e., no password) when connecting from postgres_exporter, since I want to set up this kind of sidecar for many different Postgres instances (pods) and don't want to have to configure a reference to the password for each one.

I've tried leaving out the password but this hasn't worked.

Is using peer authentication to connect to a Postgres container in the same pod:

  1. possible in principle,
  2. possible using postgres_exporter and/or
  3. reasonable?

Any hints are appreciated.