Add ppa:gophers/archive manually

bionic/x86_64/Dockerfile

@@ -2,7 +2,13 @@ FROM ubuntu:bionic
 
 ENV DEBIAN_FRONTEND=noninteractive
 
-RUN add-apt-repository ppa:gophers/archive
+RUN apt-get update \
+ && apt-get -y install apt-transport-https gnupg
+
+RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 308C15A29AD198E9 
+
+RUN echo 'deb http://ppa.launchpad.net/gophers/archive/ubuntu bionic main \n\
+deb-src http://ppa.launchpad.net/gophers/archive/ubuntu bionic main' > /etc/apt/sources.list.d/gophers.list
 
 RUN apt-get update \
  && apt-get install -y eatmydata \