docker: add multi-platform support

.github/workflows/docker.yml

@@ -49,6 +49,10 @@ jobs:
         push: ${{ github.event_name != 'pull_request' }}
         tags: ${{ steps.meta.outputs.tags }}
         labels: ${{ steps.meta.outputs.labels }}
+        platforms:
+        - linux/amd64
+        - linux/arm64
+        - linux/arm/v7
 
     # Sign the Docker image
     - name: Install cosign

Dockerfile

@@ -1,26 +1,21 @@
-FROM golang:1.17 as build
+# syntax=docker/dockerfile:1.4
+FROM --platform=$BUILDPLATFORM cgr.dev/chainguard/go:latest as build
 LABEL maintainer="Will Norris <will@willnorris.com>"
 
-RUN useradd -u 1001 go
-
 WORKDIR /app
-
 COPY go.mod go.sum ./
 RUN go mod download
 
 COPY . .
 
-RUN CGO_ENABLED=0 GOOS=linux go build -v ./cmd/imageproxy
+ARG TARGETOS
+ARG TARGETARCH
+RUN CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH go build -v ./cmd/imageproxy
 
-FROM scratch
+FROM cgr.dev/chainguard/static:latest
 
-COPY --from=build /etc/passwd /etc/passwd
-COPY --from=build /usr/share/zoneinfo /usr/share/zoneinfo
-COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 COPY --from=build /app/imageproxy /app/imageproxy
 
-USER go
-
 CMD ["-addr", "0.0.0.0:8080"]
 ENTRYPOINT ["/app/imageproxy"]