anchor.diff:      cd .. && \
       rm -rf v${PROTOC_VERSION}.zip protobuf-${PROTOC_VERSION}
   
  -ARG SWIFT_PLATFORM=ubuntu18.04
   ARG SWIFT_BRANCH=swift-5.0.1-release
   ARG SWIFT_VERSION=swift-5.0.1-RELEASE
   
  
positive.code:       python3 \
        tzdata \
        unzip \
        zlib1g-dev && \
      rm -r /var/lib/apt/lists/*
  
  
negative.code:     SWIFT_BRANCH=$SWIFT_BRANCH \
      SWIFT_VERSION=$SWIFT_VERSION
  
  RUN curl -O -L https://swift.org/builds/${SWIFT_BRANCH}/ubuntu1804/${SWIFT_VERSION}/${SWIFT_VERSION}-ubuntu18.04.tar.gz && \
      curl -O -L https://swift.org/builds/${SWIFT_BRANCH}/ubuntu1804/${SWIFT_VERSION}/${SWIFT_VERSION}-ubuntu18.04.tar.gz.sig && \
      wget -q -O - https://swift.org/keys/all-keys.asc | gpg --import - && \
      gpg --keyserver hkp://pool.sks-keyservers.net --refresh-keys Swift && \
      gpg --batch --verify --quiet ${SWIFT_VERSION}-ubuntu18.04.tar.gz.sig ${SWIFT_VERSION}-ubuntu18.04.tar.gz && \
      tar -xzf ${SWIFT_VERSION}-ubuntu18.04.tar.gz --directory / --strip-components=1 && \
      rm -r ${SWIFT_VERSION}-ubuntu18.04.tar.gz.sig ${SWIFT_VERSION}-ubuntu18.04.tar.gz && \
      chmod -R o+r /usr/lib/swift
  
  RUN swift --version
  