Fixed showing of author ids

Signed-off-by: kolaente <konrad@kola-entertainments.de>

models/book.go

@@ -37,6 +37,7 @@ func GetBookById(ID int64) (book Book, exists bool, err error)  {
 	var authors []Author
 	err = x.
 	Table("authors_books").
+		Select("authors.*").
 		Join("INNER", "authors", "authors_books.author_id = authors.id").
 		Where("book_id = ?", book.ID).
 		Find(&authors)