Run docker-compose command without exiting

I am using a postgres image and i need to start ssh service on start.
The problem is that if I run a command in docker-compose file the proccess exits with code 0.

How can I start ssh service but keep postgres serice active too?

DOCKER FILE:

FROM postgres:13

RUN apt update && apt install  openssh-server sudo -y
RUN  echo 'root:password' | chpasswd
RUN sed -i 's/#PermitRootLogin prohibit-password/PermitRootLogin yes/g' /etc/ssh/sshd_config

DOCKER-COMPOSE FILE:

postgres:
    container_name: db_postgres
    command: sh -c "service ssh start "
    image: postgresc
    build:
      context: ../backend_apollo_server_express
      dockerfile: Dockerfile.database
    environment:
      - "POSTGRES_USER=lims"
      - "POSTGRES_PASSWORD=lims"
    volumes:
      - /home/javier/lims/dockerVolumes/db:/var/lib/postgresql/data
      - "/etc/timezone:/etc/timezone:ro"
      - "/etc/localtime:/etc/localtime:ro"
    ports:
      - 5434:5432