code: func multiErrorFromErrors(ch <-chan error) error {
  	if ch == nil {
  		return nil
  	}
  	ret := errors.MultiError(nil)
  	for e := range ch {
  		if e == nil {
  			continue
  		}
  		ret = append(ret, e)
  	}
  	if len(ret) == 0 {
  		return nil
  	}
  	return ret
  }
docs: // multiErrorFromErrors takes an error-channel, blocks on it, and returns
  // a MultiError for any errors pushed to it over the channel, or nil if
  // all the errors were nil.