How to use DispatchQueue to wait for a file to be created in Swift

Question

I'm developing an app that needs to wait for files to be created in the disk in order to continue.

After obtaining the array of paths from the json file, I need the app to:

• Show a progress bar
• Wait for each file to be created in order
• Update the progress bar after each file is created

The problem is that when I use a .sync queue, the UI never shows and is waiting for all the files to be created, and if I use a .async queue, the UI shows and the for loop runs all the queues concurrently

do {
    let jsonData = try Data(contentsOf: jsonFilePathURL)
    let jsonDecoder = JSONDecoder()
    let steps = try jsonDecoder.decode(Response.self, from: jsonData)
    
    let totalStepsCount = steps.steps.count
    
    initializeProgressBar(stepsCount:totalStepsCount)
    
    // Run a loop for each file to watch
    for step in steps.steps {
        waitForFileToBeCreated(path: step.Path) 
    }

I use this to wait for each file to be created.

func waitForFileToBeCreated(path:String) {
    let group = DispatchGroup()
    group.enter()
    
    DispatchQueue.global(qos: .default).async {
        
        while !FileManager.default.fileExists(atPath: path) {
                // Wait for the file to be created
                Thread.sleep(forTimeInterval: 0.1)
            }
        
        group.leave()
        
    }
    group.wait()
    
}