Fix the check if the book is active

lib/database/books.go

@@ -159,7 +159,7 @@ func (db *pgDB) ActiveBook(id string) error {
 func (db *pgDB) IsBookActive(id string) bool {
 	var active []bool
 	err := db.sql.Model(&Book{}).
-		Relation("active").
+		Column("active").
 		Where("id = ?", id).
 		Select(&active)
 	if err != nil || len(active) != 1 {