diff --git a/Dockerfile b/Dockerfile
index 812722b..de694d3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -22,6 +22,7 @@ RUN \
 		) ; \
 	fi && \
 	echo "selected prometheus branch: ${PROMETHEUS_VERSION}" && \
+	cd / && \
 	git clone \
 		--branch="${PROMETHEUS_VERSION}" \
 		--depth=1 \
@@ -33,8 +34,8 @@ FROM alpine:3
 
 COPY --from=build /prometheus/prometheus /prometheus
 
-ARG UID=1000
-ARG GID=1000
+ENV UID=1000
+ENV GID=1000
 
 CMD addgroup -g "${GID}" prometheus && \
 	adduser -D -u "${UID}" -G prometheus prometheus && \
diff --git a/README.md b/README.md
index 669b377..0c683d8 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,14 @@
 # docker-prometheus
 
-prometheus docker build
\ No newline at end of file
+prometheus docker build
+
+## build 
+```{bash}
+GO_VERSION=1.16.0 # optional
+PROMETHEUS_VERSION=2.25.0 # optional, will use latest available, if unset
+docker \
+    build \
+    --build-arg GO_VERSION="${GO_VERSION}" \
+    --build-arg PROMETHEUS_VERSION="${PROMETHEUS_VERSION}" \
+    -t prometheus:"${PROMETHEUS_VERSION}"-local .
+```
\ No newline at end of file