configmaptocrs: improve docker build cache

Signed-off-by: Antonio Pitasi <[email protected]>

configmaptocrs/Dockerfile

@@ -1,40 +1,38 @@
 # syntax=docker/dockerfile:1.2
 
 FROM --platform=$BUILDPLATFORM docker.io/golang:1.20.10 AS builder
-ARG GIT_COMMIT=dev
-ARG GIT_BRANCH=dev
 WORKDIR $GOPATH/go.universe.tf/metallb
 
-# Cache the downloads
-COPY go.mod go.sum ./
-RUN go mod download
-
-# COPY internals
-COPY internal internal
-COPY api api
-
-# COPY configmaptocrs
-COPY configmaptocrs/*.go configmaptocrs/
+RUN --mount=type=cache,target=/go/pkg/mod/ \
+    --mount=type=bind,source=go.sum,target=go.sum \
+    --mount=type=bind,source=go.mod,target=go.mod \
+    go mod download -x
 
+ARG GIT_COMMIT=dev
+ARG GIT_BRANCH=dev
 ARG TARGETARCH
 ARG TARGETOS
 ARG TARGETPLATFORM
 
-# have to manually convert as building the different arms can cause issues
 # Extract variant
+# have to manually convert as building the different arms can cause issues
 RUN case ${TARGETPLATFORM} in \
   "linux/arm/v6") export VARIANT="6" ;; \
   "linux/arm/v7") export VARIANT="7" ;; \
   *) export VARIANT="" ;; \
   esac
 
-# Cache builds directory for faster rebuild
 RUN --mount=type=cache,target=/root/.cache/go-build \
-  --mount=type=cache,target=/go/pkg \
+  --mount=type=cache,target=/go/pkg/mod \
+  --mount=type=bind,source=go.sum,target=go.sum \
+  --mount=type=bind,source=go.mod,target=go.mod \
+  --mount=type=bind,source=internal,target=internal \
+  --mount=type=bind,source=api,target=api \
+  --mount=type=bind,source=configmaptocrs,target=configmaptocrs \
   CGO_ENABLED=0 GOOS=$TARGETOS GOARCH=$TARGETARCH GOARM=$VARIANT \
   go build -v -o /build/configmaptocrs \
   -ldflags "-X 'go.universe.tf/metallb/internal/version.gitCommit=${GIT_COMMIT}' -X 'go.universe.tf/metallb/internal/version.gitBranch=${GIT_BRANCH}'" \
-  go.universe.tf/metallb/configmaptocrs
+  ./configmaptocrs
 
 FROM docker.io/alpine:latest