anchor.diff:  RUN apt-get update && apt-get -y install wget curl git build-essential autoconf automake libtool pkg-config gnutls-bin sudo vim
   RUN apt-get install -q -y libmysqld-dev
   
  -# install go1.13.3
  -RUN wget https://dl.google.com/go/go1.13.3.linux-amd64.tar.gz && tar -C /usr/local -xzf go1.13.3.linux-amd64.tar.gz
  +# install go1.13.5
  +RUN wget https://dl.google.com/go/go1.13.5.linux-amd64.tar.gz && tar -C /usr/local -xzf go1.13.5.linux-amd64.tar.gz
   RUN mkdir $HOME/go
   ENV PATH $PATH:/usr/local/go/bin
   ENV GOPATH $HOME/go
  
positive.code: FROM ubuntu:16.04
  
  USER root
  ENV HOME /home
  
negative.code: WORKDIR $HOME
  RUN git clone https://github.com/obgm/libcoap.git
  WORKDIR $HOME/libcoap
  RUN git checkout 6fc3a7315f6629d804cc7928004cddeb4a84443c
  RUN ./autogen.sh
  RUN ./configure --disable-documentation --with-openssl
  RUN make && make install
  