Put the service in file: /lib/systemd/system/oyunkeyf.service
Service:
[Unit]
Description=Oyunkeyf Service
[Service]
Type=simple
WorkingDirectory=/home/eguneys/oyun
ExecStart=/home/eguneys/oyun/bin/oyun -Dhttp.port=9000 -Dconfig.file=/home/eguneys/oyun/application.conf -Dplay.crypto.secret="insertsecrethere"
Restart=always
[Install]
WantedBy=multi-user.target