private function loadTGTfromFile($tgtStorageLocation)
    {
        $tgtStorageData = json_decode(file_get_contents($tgtStorageLocation), true);

        if ($tgtStorageData['username']) {
            $this->casUsername = $tgtStorageData['username'];
        } else {
            throw new \Exception('TGT storage missing "username" value!', 551);
        }
        if ($tgtStorageData['server']) {
            $this->casServer = $tgtStorageData['server'];
        } else {
            throw new \Exception('TGT storage missing "server" value!', 552);
        }
        if ($tgtStorageData['context']) {
            $this->casRESTcontext = $tgtStorageData['context'];
        } else {
            throw new \Exception('TGT storage missing "context" value!', 552);
        }
        if ($tgtStorageData['TGT']) {
            $this->tgt = $tgtStorageData['TGT'];
            $this->tgtLocation = $this->casServer . $this->casRESTcontext . '/' . $this->tgt;
        } else {
            throw new \Exception('TGT storage missing "TGT" value!', 552);
        }
    }