anchor.diff:      SWIFT_BRANCH=$SWIFT_BRANCH \
       SWIFT_VERSION=$SWIFT_VERSION
   
  -RUN SWIFT_URL=https://swift.org/builds/$SWIFT_BRANCH/$(echo "$SWIFT_PLATFORM" | tr -d .)/$SWIFT_VERSION/$SWIFT_VERSION-$SWIFT_PLATFORM.tar.gz && \
  -    curl -fSsL $SWIFT_URL -o swift.tar.gz && \
  -    curl -fSsL $SWIFT_URL.sig -o swift.tar.gz.sig && \
  -    export GNUPGHOME="$(mktemp -d)" && \
  -    set -e; \
  -        for key in \
  -      # pub   4096R/ED3D1561 2019-03-22 [expires: 2021-03-21]
  -      #       Key fingerprint = A62A E125 BBBF BB96 A6E0  42EC 925C C1CC ED3D 1561
  -      # uid                  Swift 5.x Release Signing Key <swift-infrastructure@swift.org
  -          A62AE125BBBFBB96A6E042EC925CC1CCED3D1561 \
  -        ; do \
  -          gpg --quiet --keyserver ha.pool.sks-keyservers.net --recv-keys "$key"; \
  -        done && \
  -    gpg --batch --verify --quiet swift.tar.gz.sig swift.tar.gz && \
  -    tar -xzf swift.tar.gz --directory / --strip-components=1 && \
  -    rm -r "$GNUPGHOME" swift.tar.gz.sig swift.tar.gz && \
  +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
  
positive.code:     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
  
  
negative.code:       python3 \
        tzdata \
        unzip \
        wget \
        zlib1g-dev && \
      rm -r /var/lib/apt/lists/*
  
  