added systemd instructions

contrib/gonic.service

@@ -0,0 +1,28 @@
+[Unit]
+Description=Gonic service
+ConditionPathExists=/var/gonic/gonic
+After=network.target
+
+[Service]
+Type=simple
+User=gonic
+Group=gonic
+LimitNOFILE=1024
+
+Restart=on-failure
+RestartSec=10
+
+WorkingDirectory=/var/gonic/
+ExecStart=/var/gonic/gonic -config-path /var/gonic/config
+
+# make sure log directory exists and owned by syslog
+PermissionsStartOnly=true
+ExecStartPre=/bin/mkdir -p /var/log/gonic
+ExecStartPre=/bin/chown syslog:adm /var/log/gonic
+ExecStartPre=/bin/chmod 755 /var/log/gonic
+StandardOutput=syslog
+StandardError=syslog
+SyslogIdentifier=sleepservice
+
+[Install]
+WantedBy=multi-user.target