Open Radar

 
Same as https://bugreport.apple.com/web/?problemID=37714680

I'm trying to get the progress by KVO's on URLSessionDataTask's progress variable which is available in iOS 11. But I see that for downloads, I'm getting the exact progress but for uploads, I only get progress of 0, 0.95 and 1. 
I'm using below sample code (https://github.com/simplyi/ImageUploadExampleWithProgressBar), and changed it for my needs as in here.
https://stackoverflow.com/questions/48874967/ios-11-urlsessiondatatasks-progress-variable-is-not-showing-right-progress created.

Steps to Reproduce:
I'm using below sample code (https://github.com/simplyi/ImageUploadExampleWithProgressBar), and changed it for my needs 

Create a session and a sessionDataTask to upload a file as below. And start KVO 

let configuration = URLSessionConfiguration.default
    let session = URLSession(configuration: configuration)
    let task = session.dataTask(with: request) { (data, urlResp, error) in
        print("\(String(describing: data))")
    }
    if #available(iOS 11.0, *) {
        task.progress.addObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), options: [.new], context: &progressKVOContext)
        print("KVO set here")

    } else {
        // Fallback on earlier versions
    }
let configuration = URLSessionConfiguration.default
    let session = URLSession(configuration: configuration)
    let task = session.dataTask(with: request) { (data, urlResp, error) in
        print("\(String(describing: data))")
    }
    if #available(iOS 11.0, *) {
        task.progress.addObserver(self, forKeyPath: #keyPath(Progress.fractionCompleted), options: [.new], context: &progressKVOContext)
        print("KVO set here")

    } else {
        // Fallback on earlier versions
    }
    task.resume()


override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if context == &progressKVOContext && keyPath == #keyPath(Progress.fractionCompleted), let progress = object as? Progress {
        var progressFractionCompleted = (progress.totalUnitCount == -1) ? 1.0 : progress.fractionCompleted

        print("progressFractionCompleted = \(progressFractionCompleted)")
    } else {
        super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)
    }
}

Expected Results:
I should get exact upload progress printed.

Actual Results:
I only see a progress of 0, 0.95 and 1 % 

Version/Build:
iOS 11