- There is a webservice running in a Docker container.
 - This webservice relies on big json files to boot.
 
I create a Docker volume to store the json files with docker volume create my-api-files.
Here is the docker-compose file for the webservice:
version: '3'
services:
  my-api:
    image: node:alpine
    expose:
      - ${NODE_PORT}
    volumes:
      - ./:/api
      - my-api-files:/files
    working_dir: /api
    command: npm run start
volumes: 
  my-api-files: 
    external: true
Now, how can I copy the json files to the my-api-files docker volume before to start the the webservice with docker-compose up?