let url = NSURL(string: "https://website.com/api/loginauth?username=(usernameField.text)&password=(passwordField.text)")
let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
let request = NSURLRequest(URL: url!)

fatal error: unexpectedly found nil while unwrapping an Optional value

let url = NSURL(string: "https://website.com/api/loginauth?username=(usernameField.text!)&password=(passwordField.text!)")
let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration())
let request = NSURLRequest(URL: url!)