Setup docker image build action (#20)

.github/workflows/docker.yml

@@ -0,0 +1,51 @@
+name: Docker Build
+
+on:
+  push:
+    branches:
+      - "**"
+    tags:
+      - "v**"
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@v1
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=sha
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

.github/workflows/rust.yml

@@ -16,7 +16,7 @@ jobs:
   build:
     strategy:
       matrix:
-        platform: [ ubuntu-latest, macos-latest, windows-latest ]
+        platform: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.platform }}
     steps:
       - uses: actions/checkout@v2

Dockerfile

@@ -0,0 +1,15 @@
+# syntax=docker/dockerfile:experimental
+
+FROM rust:1.60-slim-buster as builder
+WORKDIR /src
+
+COPY . .
+RUN --mount=type=cache,target=target \
+    mkdir -p /out \
+    && (cd relay && cargo build -p relay --features metrics-prometheus --release) \
+    && mv target/release/relay /out/relay
+
+FROM debian:buster-slim
+RUN apt-get update && apt-get install -y ca-certificates libc6 && rm -rf /var/lib/apt/lists/*
+COPY --from=builder /out/relay /usr/local/bin/relay
+CMD ["relay"]