Reduce pulsar-test-latest-version docker image size (apache#9627)

- smaller image size makes it feasible to build the image once and share
  it between the different parallel integration test jobs. This will
  help improve the Pulsar CI in the future.

Solution:
- build go-lang examples in a separate temporary layer
- cleanup files as last steps
  - requires "-Ddockerfile.build.squash=true" (uses "docker build --squash")
    to reduce the final image size. This is not part of this change
    since the image size isn't important until images are transferred over
    the network. Squashing the image would just add overhead to the current build.

tests/docker-images/latest-version-image/Dockerfile

@@ -17,6 +17,36 @@
 # under the License.
 #
 
+# build go lang examples first in a separate layer
+
+FROM apachepulsar/pulsar-all:latest as pulsar-function-go
+
+USER root
+
+RUN rm -rf /var/lib/apt/lists/* && apt-get update
+RUN apt-get install -y procps curl git
+
+ENV GOLANG_VERSION 1.13.3
+
+RUN curl -sSL https://storage.googleapis.com/golang/go$GOLANG_VERSION.linux-amd64.tar.gz \
+		| tar -v -C /usr/local -xz
+
+# RUN wget https://dl.google.com/go/go1.13.3.linux-amd64.tar.gz && tar -xvf go1.13.3.linux-amd64.tar.gz && mv go /usr/local
+# RUN export GOROOT=/usr/local/go && export GOPATH=$HOME/go && export PATH=$GOPATH/bin:$GOROOT/bin:$PATH
+# RUN echo "export GOROOT=/usr/local/go" >> ~/.profile && echo "export GOPATH=$HOME/go" >> ~/.profile && echo "export PATH=$GOPATH/bin:$GOROOT/bin:$PATH" >> ~/.profile
+
+ENV PATH /usr/local/go/bin:$PATH
+
+RUN mkdir -p /go/src /go/bin && chmod -R 777 /go
+ENV GOROOT /usr/local/go
+ENV GOPATH /go
+ENV PATH /go/bin:$PATH
+
+COPY target/pulsar-function-go/ /go/src/github.com/apache/pulsar/pulsar-function-go
+RUN cd /go/src/github.com/apache/pulsar/pulsar-function-go && go install ./...
+RUN cd /go/src/github.com/apache/pulsar/pulsar-function-go/pf && go install
+RUN cd /go/src/github.com/apache/pulsar/pulsar-function-go/examples && go install ./...
+
 FROM apachepulsar/pulsar-all:latest
 
 # Switch to run as the root user to simplify building container and then running
@@ -27,7 +57,7 @@ USER root
 
 RUN rm -rf /var/lib/apt/lists/* && apt update
 
-RUN apt-get clean && apt-get update && apt-get install -y supervisor vim procps curl git
+RUN apt-get clean && apt-get update && apt-get install -y supervisor vim procps curl
 
 RUN mkdir -p /var/log/pulsar && mkdir -p /var/run/supervisor/ && mkdir -p /pulsar/ssl
 
@@ -48,36 +78,32 @@ COPY scripts/init-cluster.sh scripts/run-global-zk.sh scripts/run-local-zk.sh \
      /pulsar/bin/
 
 # copy python test examples
-
 RUN mkdir -p /pulsar/instances/deps
-
-ENV GOLANG_VERSION 1.13.3
-
-RUN curl -sSL https://storage.googleapis.com/golang/go$GOLANG_VERSION.linux-amd64.tar.gz \
-		| tar -v -C /usr/local -xz
-
-# RUN wget https://dl.google.com/go/go1.13.3.linux-amd64.tar.gz && tar -xvf go1.13.3.linux-amd64.tar.gz && mv go /usr/local
-# RUN export GOROOT=/usr/local/go && export GOPATH=$HOME/go && export PATH=$GOPATH/bin:$GOROOT/bin:$PATH
-# RUN echo "export GOROOT=/usr/local/go" >> ~/.profile && echo "export GOPATH=$HOME/go" >> ~/.profile && echo "export PATH=$GOPATH/bin:$GOROOT/bin:$PATH" >> ~/.profile
-
-ENV PATH /usr/local/go/bin:$PATH
-
-RUN mkdir -p /go/src /go/bin && chmod -R 777 /go
-ENV GOROOT /usr/local/go
-ENV GOPATH /go
-ENV PATH /go/bin:$PATH
-
 COPY python-examples/exclamation_lib.py /pulsar/instances/deps/
 COPY python-examples/exclamation_with_extra_deps.py /pulsar/examples/python-examples/
 COPY python-examples/exclamation.zip /pulsar/examples/python-examples/
 COPY python-examples/producer_schema.py /pulsar/examples/python-examples/
 COPY python-examples/consumer_schema.py /pulsar/examples/python-examples/
 COPY python-examples/exception_function.py /pulsar/examples/python-examples/
 
-COPY target/pulsar-function-go/ /go/src/github.com/apache/pulsar/pulsar-function-go
-RUN cd /go/src/github.com/apache/pulsar/pulsar-function-go && go install ./...
-RUN cd /go/src/github.com/apache/pulsar/pulsar-function-go/pf && go install
-RUN cd /go/src/github.com/apache/pulsar/pulsar-function-go/examples && go install ./...
-
+# copy java test examples
 COPY target/java-test-functions.jar /pulsar/examples/
-RUN cp -a /go/bin/. /pulsar/examples/go-examples/
+
+# copy go test examples
+COPY --from=pulsar-function-go /go/bin /pulsar/examples/go-examples
+
+# change ownership of files
+RUN chown -R pulsar:0 /pulsar && chmod -R g=u /pulsar
+
+# remove static libpulsar*.a libraries to reduce image size
+RUN rm /usr/lib/libpulsar*.a
+# remove gcc
+RUN apt-get -y remove --autoremove --purge build-essential
+
+# cleanup
+RUN apt-get -y autoremove \
+    && apt-get clean \
+    && apt-get autoclean \
+    && rm -rf /var/lib/apt/lists/*
+
+CMD bash