Make docker image unprivileged

Dockerfile

@@ -9,8 +9,14 @@ RUN make linux
 
 
 FROM alpine:3.12
-
-RUN apk update && apk add ca-certificates && rm -rf /var/cache/apk/*
+ARG UNAME="server-status"
+ARG GNAME="server-status"
+ARG UID=1000
+ARG GID=1000
 WORKDIR /server-status
 COPY --from=0 /go/src/github.com/mgerb/ServerStatus/dist/ServerStatus-linux .
 ENTRYPOINT ./ServerStatus-linux
+RUN addgroup -g ${GID} "${GNAME}" && adduser -D -u ${UID} -G "${GNAME}" "${UNAME}" &&\
+    chown "${UNAME}":"${GNAME}" -R /server-status/ &&\
+    apk update && apk add ca-certificates && rm -rf /var/cache/apk/*
+USER ${UNAME}