Dockerfile in switchery-rails-0.8.1.1 vs Dockerfile in switchery-rails-0.8.2.0

@@ -1,15 +1,15 @@
 # Switchery-rails gem Dockerfile
 #
 # How to use it
 # =============
 #
-# Visit http://blog.zedroot.org/using-docker-to-maintain-a-ruby-gem/
+# Visit https://blog.zedroot.org/2015/04/30/using-docker-to-maintain-a-ruby-gem/
 
 # ~~~~ Image base ~~~~
 # Base image with the latest Ruby only
-FROM ruby:2.3.0-slim
+FROM ruby:3.0.3-slim
 MAINTAINER Guillaume Hain [e-mail]
 
 
 # ~~~~ Set up the environment ~~~~
 ENV DEBIAN_FRONTEND noninteractive
@@ -19,10 +19,10 @@
 ADD . /gem/
 
 # ~~~~ OS Maintenance & Rails Preparation ~~~~
 # Rubygems and Bundler
 RUN apt-get update && \
-  apt-get install -y git build-essential && \
+  apt-get install -y git build-essential curl && \
   touch ~/.gemrc && \
   echo "gem: --no-ri --no-rdoc" >> ~/.gemrc && \
   gem install rubygems-update && \
   update_rubygems && \
   gem install bundler && \