channels3.go

import "golang.org/x/sync/errgroup"
...
g, ctx := errgroup.WithContext(ctx)
complete := make(chan []Store, len(locations))

for _, location := range locations {
  g.Go(fetchStores(ctx, store.Id, complete))
}
if err := g.Wait(); err != nil {
  log.Errorf("%s", err)
  return nil, err
}
...

func fetchStores(ctx context.Context, storeId int, out chan<- []Store) func() error {
	return func() error {
    response, err := h.Client.Do(req)

    if err != nil {
      errorMsg := log.Errorf("Connection failed with error %v", err)
      return nil, fmt.Errorf(errorMsg)
    }
    defer response.Body.Close()

    out <- parseResponse(response)
		return err
	}
}