anchor.diff:  ENV GOLANG_VERSION 1.12
   
   RUN wget -q -O go.tgz "https://golang.org/dl/go${GOLANG_VERSION}.linux-amd64.tar.gz" && \
  -	tar -C /usr/local -xzf go.tgz && \
  -	rm go.tgz && \
  -	export PATH="/usr/local/go/bin:$PATH"
  +  tar -C /usr/local -xzf go.tgz && \
  +  rm go.tgz && \
  +  export PATH="/usr/local/go/bin:$PATH"
   
   ENV GOPATH /go
   ENV PATH $GOPATH/bin:/usr/local/go/bin:$PATH
  
positive.code: 
  RUN curl -fsSLO https://download.docker.com/linux/static/stable/x86_64/docker-${DOCKER_VERSION}.tgz \
    && tar xzvf docker-${DOCKER_VERSION}.tgz --strip 1 \
                   -C /usr/local/bin docker/docker \
    && rm docker-${DOCKER_VERSION}.tgz
  
  USER ubuntu
  
negative.code: 
  RUN ARCH= && dpkgArch="$(dpkg --print-architecture)" \
    && case "${dpkgArch##*-}" in \
    amd64) ARCH='x64';; \
    ppc64el) ARCH='ppc64le';; \
    s390x) ARCH='s390x';; \
    arm64) ARCH='arm64';; \
    armhf) ARCH='armv7l';; \
    i386) ARCH='x86';; \
    *) echo "unsupported architecture"; exit 1 ;; \
    esac \
    # gpg keys listed at https://github.com/nodejs/node#release-keys
    && set -ex \
    && for key in \
    94AE36675C464D64BAFA68DD7434390BDBE9B9C5 \
    FD3A5288F042B6850C66B31F09FE44734EB7990E \
    71DCFD284A79C3B38668286BC97EC7A07EDE3FC1 \
    DD8F2338BAE7501E3DD5AC78C273792F7D83545D \
    C4F0DFFF4E8C1A8236409D08E73BC641CC11F4C8 \
    B9AE9905FFD7803F25714661B63B535A4C206CA9 \
    77984A986EBC2AA786BC0F66B01FBB92821C587A \
    8FCCA13FEF1D0C2E91008E09770F7A9A5AE15600 \
    4ED778F539E3634C779C87C6D7062848A1AB005C \
    A48C2BEE680E841632CD4E44F07496B3EB3C1762 \
    B9E2F5981AA6E0CD28160D9FF13993A75599653C \
    ; do \
    gpg --batch --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys "$key" || \
    gpg --batch --keyserver hkp://ipv4.pool.sks-keyservers.net --recv-keys "$key" || \
    gpg --batch --keyserver hkp://pgp.mit.edu:80 --recv-keys "$key" ; \
    done \
    && curl -fsSLO --compressed "https://nodejs.org/dist/v$NODE_VERSION/node-v$NODE_VERSION-linux-$ARCH.tar.xz" \
    && curl -fsSLO --compressed "https://nodejs.org/dist/v$NODE_VERSION/SHASUMS256.txt.asc" \
  