code: func (c *ComputeUtil) deleteDisk() error {
  	disk, _ := c.disk()
  	if disk == nil {
  		return nil
  	}
  
  	log.Infof("Deleting disk.")
  	op, err := c.service.Disks.Delete(c.project, c.zone, c.diskName()).Do()
  	if err != nil {
  		return err
  	}
  
  	log.Infof("Waiting for disk to delete.")
  	return c.waitForRegionalOp(op.Name)
  }
docs: // deleteDisk deletes the persistent disk.