func isTempErr(err error) bool {
	log.Printf("IS TEMP ERROR? %T %v", err, err)
	return true
}

for {
  err := gr.sync(ctx, token, loop)
  if loop && isTempErr(err) {
	log.Printf("Temporary error from github %v: %v", gr.ID(), err)
	time.Sleep(30 * time.Second)
	continue
  }
  log.Printf("github sync ending for %v: %v", gr.ID(), err)
	return err
}

type errCheck func(error) bool

// SyncLoop runs forever (until an error or context expiration) and
// updates the corpus as the tracked sources change.
func (c *Corpus) SyncLoop(ctx context.Context, check errCheck) error {
	if check == nil {
		check = isTempErr
	}
	return c.sync(ctx, true, check)
}

// Sync updates the corpus from its tracked sources.
func (c *Corpus) Sync(ctx context.Context, check errCheck) error {
	if check == nil {
		check = isTempErr
	}
	return c.sync(ctx, false, check)
}
func (c *Corpus) sync(ctx context.Context, loop bool, check errCheck) error {
	if _, ok := c.mutationSource.(*netMutSource); ok {
		return errors.New("maintner: can't run Corpus.Sync on a Corpus using NetworkMutationSource (did you mean Update?)")
	}

	group, ctx := errgroup.WithContext(ctx)
	for _, w := range c.watchedGithubRepos {
		gr, token := w.gr, w.token
		group.Go(func() error {
			log.Printf("Polling %v ...", gr.id)
			for {
				err := gr.sync(ctx, token, loop)
                                isTempErr := check(err)
				if loop && isTempErr {
					log.Printf("Temporary error from github %v: %v", gr.ID(), err)
					time.Sleep(30 * time.Second)
					continue
				}
				log.Printf("github sync ending for %v: %v", gr.ID(), err)
                                if isTempErr {
                                    err = nil
                                }
				return err
			}
		})
	}
  // Rest of function similarly calls check
}