Add production stage to Dockerfile and tidy up

Dockerfile

@@ -1,38 +1,37 @@
 ARG BUILDERIMAGE="golang:1.22"
 ARG BASEIMAGE="gcr.io/distroless/static:nonroot"
 
-FROM ${BUILDERIMAGE} as builder
+FROM ${BUILDERIMAGE} AS builder
 
-ARG LDFLAGS
-
-ENV GO111MODULE=on \
-  CGO_ENABLED=0
+ENV CGO_ENABLED=0
 
 WORKDIR /app
 
-COPY . .
-
-# --- This block can be replaced by `RUN go mod download` when github.com/docker/attest is public
+# --- This block can be removed when github.com/docker/attest is public
 ENV GOPRIVATE="github.com/docker/attest"
-RUN --mount=type=cache,target=$GOPATH/pkg/mod --mount=type=secret,id=GITHUB_TOKEN <<EOT
+RUN --mount=type=secret,id=GITHUB_TOKEN <<EOT
   set -e
   GITHUB_TOKEN=${GITHUB_TOKEN:-$(cat /run/secrets/GITHUB_TOKEN)}
   if [ -n "$GITHUB_TOKEN" ]; then
     echo "Setting GitHub access token"
     git config --global "url.https://x-access-token:${GITHUB_TOKEN}@github.com.insteadof" "https://github.com"
   fi
-  go mod download
 EOT
 # ---
 
-RUN --mount=type=cache,target=$GOPATH/pkg/mod --mount=type=cache,target=/root/.cache/go-build make build
+RUN --mount=type=bind,source=.,target=/app \
+    --mount=type=cache,target=$GOPATH/pkg/mod \
+    --mount=type=cache,target=/root/.cache/go-build \
+    go build -o /bin/attest main.go
 
-FROM ${BASEIMAGE}
+FROM ${BASEIMAGE} AS production
 
-COPY --from=builder /app/bin/attest /
-
-COPY --from=builder --chown=65532:65532 /app/certs/tls.crt /app/certs/tls.key /certs/
+COPY --from=builder /bin/attest /
 
 USER 65532:65532
 
 ENTRYPOINT ["/attest"]
+
+FROM production AS dev
+
+COPY certs/tls.crt certs/tls.key /certs/