Gemfile in rails_failover-0.3.0 vs Gemfile in rails_failover-0.4.0

@@ -14,6 +14,7 @@
 group :development, :test do
   gem 'byebug'
   gem 'redis', '~> 4.1'
   gem 'pg', '~> 1.2'
   gem 'activerecord', '~> 6.0'
+  gem 'rack'
 end