在Swift中，我有一个函数可以递归地复制文件夹，并使用异步调用。我想添加一个完成处理程序。有什么优雅的解决方案吗？

import Foundation

func copyFolderRecursively(atPath sourcePath: String, toPath destinationPath: String, completion: @escaping () -> Void) {
    DispatchQueue.global().async {
        do {
            let fileManager = FileManager.default
            let sourceURL = URL(fileURLWithPath: sourcePath)
            let destinationURL = URL(fileURLWithPath: destinationPath)
            
            try fileManager.createDirectory(at: destinationURL, withIntermediateDirectories: true, attributes: nil)
            
            let fileURLs = try fileManager.contentsOfDirectory(at: sourceURL, includingPropertiesForKeys: nil)
            
            for fileURL in fileURLs {
                let destinationFileURL = destinationURL.appendingPathComponent(fileURL.lastPathComponent)
                
                try fileManager.copyItem(at: fileURL, to: destinationFileURL)
                
                if fileManager.fileExists(atPath: fileURL.path) && fileManager.fileExists(atPath: destinationFileURL.path) {
                    try fileManager.removeItem(at: fileURL)
                }
            }
            
            DispatchQueue.main.async {
                completion()
            }
        } catch {
            print("Error copying folder: \(error)")
        }
    }
}

// 使用示例
copyFolderRecursively(atPath: "/path/to/source/folder", toPath: "/path/to/destination/folder") {
    print("Folder copied successfully!")
}