Create a new rails app using

1. Rename .env.example with you own values

2. Create your src directory

mkdir src

3. Run the following command to generate a new rails app

docker-compose run --rm webapp rails new . -d postgresql

4. Replace database with database.yml.example

cp database.yml.example src/config/database.yml

5. Create databases

docker-compose run --rm webapp rails db:create

6. Run rails server

docker-compose up