anchor.diff:  RUN tar --strip=1 -C $GOROOT_BOOTSTRAP -vxzf /tmp/go.tar.gz
   
   # Fetch Go source for tag $GO_VERSION.
  -RUN git clone --depth=1 --branch=$GO_VERSION https://go.googlesource.com/go /usr/local/go
  +RUN git clone --depth=1 --branch=$GO_BOOTSTRAP_VERSION https://go.googlesource.com/go /usr/local/go
   # Apply the fake time and fake filesystem patches.
   RUN patch /usr/local/go/src/runtime/rt0_nacl_amd64p32.s /usr/local/playground/enable-fake-time.patch
   RUN cd /usr/local/go && $GOROOT_BOOTSTRAP/bin/go run misc/nacl/mkzip.go -p syscall /usr/local/playground/fake_fs.lst src/syscall/fstest_nacl.go
  
positive.code: ENV GOPATH /go
  ENV PATH /usr/local/go/bin:$GOPATH/bin:$PATH
  ENV GOROOT_BOOTSTRAP /usr/local/gobootstrap
  ENV GO_BOOTSTRAP_VERSION go1.13
  ARG GO_VERSION=go1.13
  ENV GO_VERSION ${GO_VERSION}
  
  # Fake time
  
negative.code: ENV BUILD_DEPS 'curl git gcc patch libc6-dev ca-certificates'
  RUN apt-get update && apt-get install -y --no-install-recommends ${BUILD_DEPS}
  
  RUN cd /usr/local && git clone https://go.googlesource.com/go go1.14 && cd go1.14 && git reset --hard $GO_VERSION
  WORKDIR /usr/local/go1.14/src
  RUN ./make.bash
  ENV GOROOT /usr/local/go1.14
  