refactor(flagd): update profile.Dockerfile with buildkit caching

flagd/profile.Dockerfile

@@ -2,33 +2,40 @@
 # Build the manager binary
 FROM --platform=$BUILDPLATFORM golang:1.20-alpine AS builder
 
-WORKDIR /workspace
+WORKDIR /src
+
 ARG TARGETOS
 ARG TARGETARCH
 ARG VERSION
 ARG COMMIT
 ARG DATE
 
-# Copy source code
-COPY flagd/ flagd
-COPY core/ core
-
-# Setup go workspace 
-RUN go work init
-RUN go work use ./flagd
-RUN go work use ./core
-
-# Go get dependencies
-RUN cd flagd && go mod download
+# Download dependencies as a separate step to take advantage of Docker's caching.
+# Leverage a cache mount to /go/pkg/mod/ to speed up subsequent builds.
+# Leverage bind mounts to go.sum and go.mod to avoid having to copy them into
+# the container.
+RUN --mount=type=cache,target=/go/pkg/mod/ \
+    --mount=type=bind,source=./core/go.mod,target=./core/go.mod \
+    --mount=type=bind,source=./core/go.sum,target=./core/go.sum \
+    --mount=type=bind,source=./flagd/go.mod,target=./flagd/go.mod \
+    --mount=type=bind,source=./flagd/go.sum,target=./flagd/go.sum \
+    go work init ./core ./flagd && go mod download
 
-# Build with profiler
-RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -a -ldflags "-X main.version=${VERSION} -X main.commit=${COMMIT} -X main.date=${DATE}" -o flagd-build flagd/main.go flagd/profiler.go
+# Build the application.
+# Leverage a cache mount to /go/pkg/mod/ to speed up subsequent builds.
+# Leverage a bind mount to the current directory to avoid having to copy the
+# source code into the container.
+RUN --mount=type=cache,target=/go/pkg/mod/ \
+    --mount=type=cache,target=/root/.cache/go-build \
+    --mount=type=bind,source=./core,target=./core \
+    --mount=type=bind,source=./flagd,target=./flagd \
+    CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -a -ldflags "-X main.version=${VERSION} -X main.commit=${COMMIT} -X main.date=${DATE}" -o /bin/flagd-build ./flagd/main.go ./flagd/profiler.go
 
 # Use distroless as minimal base image to package the manager binary
 # Refer to https://github.com/GoogleContainerTools/distroless for more details
 FROM gcr.io/distroless/static:nonroot
 WORKDIR /
-COPY --from=builder /workspace/flagd-build .
+COPY --from=builder /bin/flagd-build .
 USER 65532:65532
 
 ENTRYPOINT ["/flagd-build"]