I have a similar issue with the error message : Cloud SQL connection failed. Please see https://cloud.google.com/sql/docs/mysql/connect-run for additional details: certificate had CN "", expected "<project_id>:<instance_id>"

I have a simple setup where I deploy my Ruby backend API on a Cloud RUN Service using an artifact, and I connect it to a PostgreSQL database on Cloud SQL. I try to connect both through a UNIX socket as it seems to be the correct way to do it (rather than TCP).

In my Cloud Run configuration, I specifically selected the database instance to automatically establish the socket in the background (according to Google Cloud documentation). According to the documentation, I'm not supposed to setup a Cloud Auth Proxy with this setup, however, I can't make it work, the connection always fails.