private function login(ServerRequestInterface $request, &$username)
    {
        //Check header
        $authorization = self::parseAuthorizationHeader($request->getHeaderLine('Authorization'));

        if (!$authorization) {
            return false;
        }

        //Check whether user exists
        if (!isset($this->users[$authorization['username']])) {
            return false;
        }

        $username = $authorization['username'];

        //Check authentication
        return $this->checkAuthentication($authorization, $request->getMethod(), $this->users[$username]);
    }