try nc

Author: koss822

Docker/selenium-firefox/Dockerfile

@@ -14,6 +14,7 @@ RUN  apt-get update \
 RUN update-ca-certificates
 
 # OPTIONAL: Install dumb-init (Very handy for easier signal handling of SIGINT/SIGTERM/SIGKILL etc.)
+RUN nc -zv objects.githubusercontent.com 443
 RUN wget "https://github.com/Yelp/dumb-init/releases/download/v1.2.5/dumb-init_1.2.5_amd64.deb"
 RUN dpkg -i dumb-init_*.deb
 ENTRYPOINT ["/usr/bin/dumb-init", "--"]