Add dockerfile and a github action to publish docker image

.github/workflows/docker-release.yml

@@ -0,0 +1,19 @@
+name: Publish Docker image
+on:
+  release:
+    types: [published]
+jobs:
+  push_to_registry:
+    name: Push Docker image to GitHub Packages
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v2
+      - name: Push to GitHub Packages
+        uses: docker/build-push-action@v1
+        with:
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+          registry: ghcr.io
+          repository: camptocamp/cups_exporter
+          tag_with_ref: true

Dockerfile

@@ -0,0 +1,17 @@
+FROM golang:1.13 as builder
+
+WORKDIR /build
+ADD . /build
+RUN go build -o cups_exporter main.go
+
+FROM golang:1.13
+
+LABEL maintainer="lenny.consuegra@camptocamp.com"
+
+ENV CUPS_URI "https://localhost:631"
+
+COPY --from=builder /build/cups_exporter /bin/cups_exporter
+
+EXPOSE 9329
+
+CMD [ "/bin/sh", "-c", "/bin/cups_exporter -cups.uri ${CUPS_URI}" ]