Permission issue with PostgreSQL in docker container

I'm trying to run a docker image with PostgreSQL that has a volume configured for persisting data.

docker-compose.yml

version: '3.1'services:  db:    image: postgres    restart: always    volumes:      - ./data:/var/lib/postgresql/data    environment:      POSTGRES_PASSWORD: example

When I start the container I see the output

fixing permissions on existing directory /var/lib/postgresql/data ... ok

and the data folder is no longer readable for me.

If I elevate myself and access the data directory I can see that the files are there. Furthermore, the command ls -ld data gives me

drwx------ 19 systemd-coredump root 4096 May 17 16:22 data

I can manually set the directory permission with sudo chmod 755 data, but that only works until I restart the container.

Why does this happen, and how can I fix it?