improve docker build caching

Author: CharlieTLe

src/checkoutservice/Dockerfile

@@ -5,22 +5,24 @@
 FROM golang:1.22-alpine AS base-build
 
 WORKDIR /build
-RUN go env -w GOMODCACHE=/root/.cache/go-build
 
+RUN apk add --no-cache protobuf-dev
+
+RUN go env -w GOMODCACHE=/root/.cache/go-build
 COPY ./src/checkoutservice/go.mod ./src/checkoutservice/go.sum ./
 RUN --mount=type=cache,target=/root/.cache/go-build go mod download
 
 COPY ./src/checkoutservice/tools.go ./
 RUN --mount=type=cache,target=/root/.cache/go-build \
     go list -e -f '{{range .Imports}}{{.}} {{end}}' tools.go | CGO_ENABLED=0 xargs go install -mod=readonly
 
-RUN apk add --no-cache protobuf-dev
+COPY ./pb ./pb
+RUN --mount=type=cache,target=/root/.cache/go-build \
+    protoc -I ./pb ./pb/demo.proto --go_out=./ --go-grpc_out=./
 
 COPY ./src/checkoutservice ./
-COPY ./pb ./pb
 RUN --mount=type=cache,target=/root/.cache/go-build \
-    protoc -I ./pb ./pb/demo.proto --go_out=./ --go-grpc_out=./ \
-    && go build -ldflags "-s -w" -o /go/bin/checkoutservice/ ./
+    go build -ldflags "-s -w" -o /go/bin/checkoutservice/ ./
 
 FROM alpine