Merge pull request #12 from jvidalallende/multistage_dockerfile

docker: use multi-stage build

Dockerfile

@@ -1,6 +1,13 @@
-FROM golang:1.20.10-alpine
+# Builder phase, includes golang toolchain
+FROM golang:1.20.11-alpine3.18 as builder
+COPY . /src
+WORKDIR /src
+RUN go build -o mq2prom ./cmd
+
+# Runtime phase, contains bare alpine plus the built binary and the config file
+# IMPORTANT: keep the alpine version on the builder and the runtime base images aligned
+FROM alpine:3.18
 RUN mkdir /mq2prom
-COPY . /mq2prom
 WORKDIR /mq2prom
-RUN go build -o mq2prom ./cmd
-CMD ./mq2prom
+COPY --from=builder /src/mq2prom /src/config.yaml .
+CMD ["./mq2prom"]