Fix rubocop issues, introduce usage of frozen literal to improve performance

config/initializers/redis.rb

@@ -1,5 +1,7 @@
-$redis = Redis.new({
+# frozen_string_literal: true
+
+Redis.current = Redis.new(
   host: ENV.fetch('REDIS_HOST') { 'localhost' },
   port: ENV.fetch('REDIS_PORT') { 6379 },
   driver: :hiredis
-})
+)