anchor.diff:  	LC_ALL=C.UTF-8 \
   	LANG=C.UTF-8 \
   	LANGUAGE=C.UTF-8 \
  -	DEBIAN_FRONTEND=noninteractive
  +	DEBIAN_FRONTEND=noninteractive \
  +	GPG_SERVERS="ha.pool.sks-keyservers.net hkp://p80.pool.sks-keyservers.net:80 keyserver.ubuntu.com hkp://keyserver.ubuntu.com:80 pgp.mit.edu"
   
   # add runtime user
   RUN \
  
positive.code: # install gosu
  RUN \
  	GOSU_VERSION=1.11 && \
  	http_proxy='' gpg --keyserver ipv4.pool.sks-keyservers.net --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4 && \
  	wget -O/usr/bin/gosu     "https://github.com/tianon/gosu/releases/download/${GOSU_VERSION}/gosu-amd64" && \
  	wget -O/usr/bin/gosu.asc "https://github.com/tianon/gosu/releases/download/${GOSU_VERSION}/gosu-amd64.asc" && \
  	gpg --verify /usr/bin/gosu.asc && \
  
negative.code: # install tini
  RUN \
  	TINI_VERSION=v0.18.0 && \
  	for server in $(shuf -e ${GPG_SERVERS}) ; do \
  		http_proxy= gpg --keyserver "$server" --recv-keys 0527A9B7 && break || : ; \
  	done && \
  	wget -O/usr/bin/tini     "https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini" && \
  	wget -O/usr/bin/tini.asc "https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini.asc" && \
  	gpg --verify /usr/bin/tini.asc && \
  