code: func (c *Client) Delete(key string, opts ...datasync.DelOption) (existed bool, err error) {
  	boltLogger.Debugf("Delete: %q", key)
  
  	prevVal, err := c.safeUpdate(&update{
  		key:   []byte(key),
  		value: nil,
  	})
  	if err != nil {
  		return false, err
  	}
  	existed = prevVal != nil
  
  	c.bumpWatchers(&watchEvent{
  		Key:       key,
  		PrevValue: prevVal,
  		Type:      datasync.Delete,
  	})
  
  	return existed, err
  }
docs: // Delete deletes given key