func read<T: Object>(entity: T.Type, filter query: String? = nil) -> [T] {
        var result: [T] = []
        
        realmSerialQueue.async { [weak self] in
            guard let self = self else {
                self?.semaphore.signal()
                return
            }
            
            let realm = try! Realm(configuration: self.configuration, queue: self.realmSerialQueue)
            
            if let query = query {
                result = realm.objects(entity).filter(query).toArray(ofType: entity)
            } else {
                result = realm.objects(entity).toArray(ofType: entity)
            }
            
            self.semaphore.signal()
        }
        
        semaphore.wait()
        
        return result
    }

func getLatestGoals() -> [Category] {
        var categoryMap: [String:Category] = [:]

        let goalEntities = realmManager.read(entity: GoalEntity.self)
                                       .sorted { $0.createdDate < $1.createdDate }
        let categoryEntities = realmManager.read(entity: CategoryEntity.self)
        
       // 바로 여기서 Realm에서 가져온 객체에 메인 스레드가 접근하기 때문에 런타임 오류 발생
        categoryEntities.forEach {
            categoryMap[$0.title] = Category(entity: $0)
        }
        
        goalEntities.forEach {
            var goal = Goal(entity: $0)
            let goalTitle = goal.title
            let photoCount = realmManager.read(entity: PhotoEntity.self, filter: "goalTitle == '\(goalTitle)'").count
            goal.progress = photoCount
            categoryMap[$0.category]?.items.append(goal)
        }
        
        return Array(categoryMap.values).sorted { $0.createdDate < $1.createdDate }
    }