chore(ci): speed up docker build

trying two things:
- speed up arm build by allowing cross-comp
- take a stab at caching builx layers

.github/workflows/docker-image.yml

@@ -32,6 +32,14 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v2
 
+      - name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
+
       - name: Get tags
         id: tags
         run: |
@@ -54,3 +62,12 @@ jobs:
           push: true
           file: ./Dockerfile
           tags: "${{ steps.tags.outputs.value }}"
+          cache-from: type=local,src=/tmp/.buildx-cache
+          cache-to: type=local,dest=/tmp/.buildx-cache-new
+
+      # https://github.com/docker/build-push-action/issues/252
+      # https://github.com/moby/buildkit/issues/1896
+      - name: Move cache to limit growth
+        run: |
+          rm -rf /tmp/.buildx-cache
+          mv /tmp/.buildx-cache-new /tmp/.buildx-cache

Dockerfile

@@ -1,8 +1,13 @@
-FROM golang:1.20-bullseye AS builder
+FROM --platform=${BUILDPLATFORM:-linux/amd64} golang:1.20-bullseye AS builder
 MAINTAINER IPFS Stewards <[email protected]>
 
 # This dockerfile builds and runs bifrost-gateway
 
+ARG TARGETPLATFORM
+ARG BUILDPLATFORM
+ARG TARGETOS
+ARG TARGETARCH
+
 ENV GOPATH      /go
 ENV SRC_PATH    $GOPATH/src/github.com/ipfs/bifrost-gateway
 ENV GO111MODULE on
@@ -34,11 +39,11 @@ RUN go mod download
 
 COPY --chown=1000:users . $SRC_PATH
 RUN git config --global --add safe.directory /go/src/github.com/ipfs/bifrost-gateway
-RUN go install
+RUN GOOS=$TARGETOS GOARCH=$TARGETARCH go build -o $GOPATH/bin/bifrost-gateway
 
 
 #------------------------------------------------------
-FROM busybox:1-glibc
+FROM --platform=${BUILDPLATFORM:-linux/amd64} busybox:1-glibc
 MAINTAINER IPFS Stewards <[email protected]>
 
 ENV GOPATH                 /go