Daniel Bochukov

Please, add to NotificationRequest ``` NotificationRequest { IncludeExtPlayerIDs []string `json:"include_external_user_ids,omitempty"` } ``` OneSignal provides a way to signal players via external_user_ids reference: https://documentation.onesignal.com/reference/create-notification

Hi, nice work! I am curious: Can you explain why In the book.go allBooks function all variables for database query rows are redeclared inside "for" loop? What about memory allocation?...