first attempt at multi-stage build

Author: adamancini

Dockerfile

@@ -1,16 +1,23 @@
-FROM golang:1.11-alpine
+FROM golang:1.11-alpine as build-swarmctl
+WORKDIR /go/src/github.com/docker
 
-RUN apk add --no-cache --update bash ca-certificates curl make git openssh-client unzip jq docker
+RUN apk add --no-cache --update bash ca-certificates curl make git openssh-client
+RUN git clone https://github.com/docker/swarmkit.git swarmkit && cd swarmkit && make bin/swarmctl && cp bin/swarmctl /usr/bin/swarmctl && rm -rf /go/src/github.com/docker/swarmkit
 
+FROM alpine:3.9 as build-protoc
 # should stay consistent with the version in .circleci/config.yml
 ARG PROTOC_VERSION=3.6.1
 # download and install protoc binary and .proto files
 RUN curl --silent --show-error --location --output protoc.zip \
   https://github.com/google/protobuf/releases/download/v$PROTOC_VERSION/protoc-$PROTOC_VERSION-linux-x86_64.zip \
   && unzip -d /usr/local protoc.zip include/\* bin/\* \
   && rm -f protoc.zip
-WORKDIR /go/src/github.com/docker
-RUN git clone https://github.com/docker/swarmkit.git swarmkit && cd swarmkit && make bin/swarmctl && cp bin/swarmctl /usr/bin/swarmctl && rm -rf /go/src/github.com/docker/swarmkit
 
+FROM alpine:3.9
+
+# WORKDIR /go/src/github.com/docker
+# RUN git clone https://github.com/docker/swarmkit.git swarmkit && cd swarmkit && make bin/swarmctl && cp bin/swarmctl /usr/bin/swarmctl && rm -rf /go/src/github.com/docker/swarmkit
+COPY --from=build-swarmctl /usr/bin/swarmctl /usr/bin/swarmctl
+COPY --from=build-protoc /usr/local/. /usr/local
 COPY ip-util-check /usr/bin
 CMD [ "/usr/bin/ip-util-check" ]