     public let request: ServiceRequest
     public let cacheFileURL: URL
     
-    public var responseData: Data? {
-        return try? Data(contentsOf: cacheFileURL)
-    }
+    public private(set) var responseData: Data?
 
     // MARK: - Initialization
 

            
            do {
                try FileManager.default.moveItem(at: localURL, to: cacheFileURL)
            } catch let error as NSError {
                aggregateError(error)
            }

        
        name = "Download Service Request Operation \(url)"
        
        let task = urlSession.downloadTask(with: urlRequest) { [weak self] (url, _, error) in
            self?.downloadFinished(url, error: error)
        }
        
