code: func GetRecipientFunc(ctx context.Context) store.RecipientCallback {
  	imf, ok := ctx.Value(ctxKeyRecipientFunc).(store.RecipientCallback)
  	if !ok || imf == nil {
  		return func(ctx context.Context, msg string, rs []string) ([]string, error) {
  			return rs, nil
  		}
  	}
  	return imf
  }
docs: // GetRecipientFunc will return the recipient callback or a default one returning
  // the unaltered list of recipients.
  // Note: will never return nil