code: func (c *Command) Close() error {
  	if err := c.check(); err != nil {
  		return err
  	}
  
  	select { // close cancel channel if it's still open
  	case <-c.cancel:
  	default:
  		close(c.cancel)
  	}
  
  	request := NewSignalRequest(c.client.url, c.shell.id, c.id, &c.client.Parameters)
  	defer request.Free()
  
  	_, err := c.client.sendRequest(request)
  	return err
  }
docs: // Close will terminate the running command