ci: 🎡 opmimize image building

Dockerfile

@@ -1,17 +1,30 @@
-FROM golang:1.23-alpine AS builder
+# Build stage
+FROM --platform=$BUILDPLATFORM golang:1.23-alpine AS builder
+
+ARG TARGETARCH
 
 WORKDIR /app
-COPY . .
 
+# Copy go mod files first for better layer caching
+COPY go.mod go.sum ./
 RUN go mod download
-RUN CGO_ENABLED=0 GOOS=linux go build -o k8s-image-updater
 
-FROM alpine:3.19
+# Copy source code
+COPY . .
 
-ENV GIN_MODE=release
+# Build with optimizations
+RUN GOARCH=${TARGETARCH} CGO_ENABLED=0 GOOS=linux go build \
+    -ldflags="-s -w" \
+    -o k8s-image-updater
 
-WORKDIR /app
-COPY --from=builder /app/k8s-image-updater .
+# Final stage
+FROM scratch
+
+# Copy SSL certificates from builder
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /app/k8s-image-updater /
+
+ENV GIN_MODE=release
 
 EXPOSE 8080
-CMD ["./k8s-image-updater"] 
+ENTRYPOINT ["/k8s-image-updater"]