DockerでRailsを環境構築する際のrails db:create がうまく機能しない(PostgreSQL)

前提・実現したいこと

rails db:creteでデータベースを作りたい

発生している問題・エラーメッセージ

rails db:create とコマンドで叩くとUnknown hostとなり、データベースが作られない。それゆえrailsのウェルカムページが表示されない。

Caused by:
PG::ConnectionBad: could not translate host name "db" to address: Unknown host

該当のソースコード

database.yml

default: &default
  adapter: postgresql
  encoding: unicode
  host: db
  username: postgres
  password: password
  pool: 5

development:
  <<: *default
  database: reruforcomapany 


test:
  <<: *default
  database: myapp_test 

production:
  <<: *default
  database: myapp_production
  username: myapp
  password: <%= ENV['MYAPP_DATABASE_PASSWORD'] %>

docker-compose.yml

version: '3'

services:
  db:
    image: postgres
    volumes:
      - postgres-data:/var/lib/postgresql/data
    environment:
      - POSTGRES_PASSWORD=password
      - POSTGRES_DB=postgres
      - POSTGRES_USER=postgres
  api:
    build: 
      context: ./api/
      dockerfile: Dockerfile
    command: /bin/sh -c "rm -f /myapp/tmp/pids/server.pid && bundle exec rails s -p 3000 -b '0.0.0.0'"
    image: rails:dev
    volumes:
      - ./api:/myapp
      - ./api/vendor/bundle:/myapp/vendor/bundle
    environment:
      TZ: Asia/Tokyo
      RAILS_ENV: development
    ports:
      - 3000:3000
    depends_on:
      - db
  front:
    build: 
      context: ./front/
      dockerfile: Dockerfile
    volumes:
      - ./front:/usr/src/app
    command: sh -c "cd react-sample && yarn start"
    ports:
      - "8000:3000"
volumes:
  postgres-data:
    driver: local

docker-compose psの実行結果(Nameは作成中のアプリ名)

Name                       Command               State           Ports
----------------------------------------------------------------------------------------
reruforcompany_api_1     entrypoint.sh /bin/sh -c r ...   Up      0.0.0.0:3000->3000/tcp
reruforcompany_db_1      docker-entrypoint.sh postgres    Up      5432/tcp
reruforcompany_front_1   docker-entrypoint.sh sh -c ...   Up      0.0.0.0:8000->3000/tcp

Dockerfile

FROM ruby:2.6
RUN apt-get update -qq && apt-get install -y nodejs postgresql-client
RUN mkdir /myapp
WORKDIR /myapp
COPY Gemfile /myapp/Gemfile
COPY Gemfile.lock /myapp/Gemfile.lock
RUN bundle install
COPY . /myapp

COPY entrypoint.sh /usr/bin/
RUN chmod +x /usr/bin/entrypoint.sh
ENTRYPOINT ["entrypoint.sh"]
EXPOSE 3000

CMD ["rails", "server", "-b", "0.0.0.0"]