code: func (m *Main) Run() error {
  	if m.Num < 2 || m.Vehicle == "" {
  		return fmt.Errorf("Need more gophers and/or vehicles.")
  	}
  	fmt.Printf("%d gophers stole my %s!\n", m.Num, m.Vehicle)
  	return nil
  }
docs: // Run implements the Runner interface so that commandeer.Run can be used with
  // Main.