title: docker-compose - service 'volumes' must be a mapping not an array
body: <p>before you mark this question as duplicate, I have looked in a lot of threads and none of them are solving the problem.</p>
  
  <p>here is my docker compose file:</p>
  
  <pre><code>version: '3'
  
  services:
    # nginx
    nginx:
      build : ./nginx
      volumes: 
        - ./site:/var/www/html
      ports:
        - '8080:80'
      depends_on:
        php
    # database
    db:
      image: mysql:5.7
      volumes:
        - db_data:/var/lib/mysql
      restart: always
      environment:
        MYSQL_ROOT_PASSWORD: bedrock123
        MYSQL_DATABASE: xyz
        MYSQL_USER: iamuser
        MYSQL_PASSWORD: iampass
      networks:
        - wpsite
  
    # php
    php:
      image: php:latest
    volumes:
      - ./site:./var/www/html
  </code></pre>
  
  <p>I am aware of probable indentation faults, and I did check for them but that doesn't seem to solve the problem.</p>