Optimize docker image (#492)

Dockerfile

@@ -4,22 +4,22 @@ ARG VERSION
 
 WORKDIR /build
 COPY . .
-RUN apk add git
-RUN CGO_ENABLED=0 go build -ldflags="-s -w -X 'github.com/prometheus/common/version.Version=$VERSION'"
+RUN apk add git \
+    && CGO_ENABLED=0 go build -ldflags="-s -w -X 'github.com/prometheus/common/version.Version=$VERSION'"
 
 
 FROM alpine:3.18.4
 
-RUN apk add --no-cache tzdata
-RUN mkdir -p /etc/dnscollector/ /var/dnscollector/
+RUN apk add --no-cache tzdata \
+    && mkdir -p /etc/dnscollector/ /var/dnscollector/ \
+    && addgroup -g 1000 dnscollector && adduser -D -H -G dnscollector -u 1000 -S dnscollector \
+    && chown dnscollector:dnscollector /var/dnscollector /etc/dnscollector
+
+USER dnscollector
 
 COPY --from=builder /build/go-dnscollector /bin/go-dnscollector
 COPY --from=builder /build/config.yml ./etc/dnscollector/config.yml
 
-RUN addgroup -g 1000 dnscollector && adduser -D -H -G dnscollector -u 1000 -S dnscollector 
-RUN chown dnscollector:dnscollector /var/dnscollector /etc/dnscollector
-USER dnscollector
-
 EXPOSE 6000/tcp 8080/tcp
 
 ENTRYPOINT ["/bin/go-dnscollector"]