DispatchGroup vs DispatchSemaphor (Swift 5)

class ViewController: UIViewController {
    
    var sampleImageURLs = ["https://yesofcorsa.com/wp-content/uploads/2016/12/4K-Black-Wallpaper-UHD.jpg","https://images.unsplash.com/photo-1551509134-2f9d4ec80a9b?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjI0MX0&auto=format&fit=crop&w=1650&q=80","https://i.picsum.photos/id/885/200/300.jpg?grayscale"]
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        checkDispatchGroup()
        checkDispatchSemaphor()
    }
    
    fileprivate func checkDispatchSemaphor() {
        let semaphore = DispatchSemaphore(value: 0)
        
        let dispatchQueue = DispatchQueue.global(qos: .background)
        
        dispatchQueue.async {
            
            self.fetchImage(self.sampleImageURLs[0]) { (_, _) in
                print("DispatchSemaphor = Finished fetching image 1")
                semaphore.signal()
            }
            semaphore.wait()
            
            self.fetchImage(self.sampleImageURLs[1]) { (_, _) in
                print("DispatchSemaphor = Finished fetching image 2")
                semaphore.signal()
            }
            semaphore.wait()
            
            self.fetchImage(self.sampleImageURLs[2]) { (_, _) in
                print("DispatchSemaphor = Finished fetching image 3")
                semaphore.signal()
            }
            semaphore.wait()
        }
    }
    
    fileprivate func checkDispatchGroup() {
        let dispatchGroup = DispatchGroup()
        
        dispatchGroup.enter()
        fetchImage(self.sampleImageURLs[0]) { (_,_) in
            print("DispatchGroup = Finished fetching image 1")
            dispatchGroup.leave()
        }
        
        dispatchGroup.enter()
        fetchImage(self.sampleImageURLs[1]) { (_,_) in
            print("DispatchGroup = Finished fetching image 2")
            dispatchGroup.leave()
        }
        
        dispatchGroup.enter()
        fetchImage(self.sampleImageURLs[2]) { (_,_) in
            print("DispatchGroup = Finished fetching image 3")
            dispatchGroup.leave()
        }
        
        dispatchGroup.notify(queue: .main) {
            print("Finished fetching images.")
        }
        print("Waiting for images to finish fetching...")
    }
    
    func fetchImage(_ imageURL: String,completion: @escaping (UIImage?, Error?) -> ()) {
        guard let url = URL(string: imageURL)
            else {
                return }
        URLSession.shared.dataTask(with: url) {
            (data, resp, err) in
            completion(UIImage(data: data ?? Data()), nil)
        }
        .resume()
    }
}