This method should start executing the given request, returning a URLSessionTask if it chooses to do so. You do not neet to call
resume()on this task, it’s supposed to already have started. It is being returned so you may be able to do additional stuff.
func perform(request: URLRequest, completionHandler: @escaping (Data?, URLResponse?, Error?) -> Void) -> URLSessionTask?
An URLRequest object that provides the URL, cache policy, request type, body data or body stream, and so on.
The completion handler to call when the load request is complete.
An already running session task