title: Heroku CLI "No command specified for process type web" when releasing container
body: <p>I am deploying a .Net Core application using Docker Containers.</p>
  
  <p>I was able to push the image successfully using <code>heroku container:push web</code></p>
  
  <p>But calling <code>heroku container:release web</code> returns <code>No command specified for process type web</code>.</p>
  
  <p>I'm a bit stumped I've tried adding <code>heroku.yml</code></p>
  
  <pre><code>setup:
    addons:
      - plan: heroku-postgresql
        as: DATABASE
  build:
    docker:
      web: Dockerfile
    config:
      ASPNETCORE_ENVIRONMENT: development
  run:
    web: dotnet Api.dll
  </code></pre>
  
  <p>On the root directory but still no luck.</p>
  
  <p>I can confirm that the image was created I'm seeing this in docker</p>
  
  <pre><code>REPOSITORY                                     TAG                 IMAGE ID            CREATED             SIZE
  registry.heroku.com/immense-temple-11020/web   latest              5cb62a9af317        16 minutes ago      272MB
  </code></pre>
  
  <p>If anyone could point me to the right direction, it would be much appreciated. Thanks!</p>