code: func (e *fileExtractor) procfile(ctx context.Context, id string) (string, error) {
  	p := ""
  
  	c, err := e.client.InspectContainer(id)
  	if err != nil {
  		return "", err
  	}
  
  	if c.Config != nil {
  		p = c.Config.WorkingDir
  	}
  
  	return path.Join(p, empire.Procfile), nil
  }
docs: // procfile returns the path to the Procfile. If the container has a WORKDIR
  // set, then this will return a path to the Procfile within that directory.