code: func (pget Pget) ErrTop(err error) error {
  	for e := err; e != nil; {
  		switch e.(type) {
  		case ignore:
  			return nil
  		case cause:
  			e = e.(cause).Cause()
  		default:
  			return e
  		}
  	}
  
  	return nil
  }
docs: // ErrTop get important message from wrapped error message