Not able to Subscribe

Hi there! Im pretty new to programming and have been taking the Multiple Chatroom lessons but....
Getting this error...can somebody help me with it?

Started GET "/cable" for ::1 at 2021-05-14 17:47:20 -0300
Started GET "/cable/" [WebSocket] for ::1 at 2021-05-14 17:47:20 -0300
Successfully upgraded to WebSocket (REQUEST_METHOD: GET, HTTP_CONNECTION: Upgrade, HTTP_UPGRADE: websocket)
Could not execute command from ({"command"=>"subscribe", "identifier"=>"{\"channel\":\"MessageChannel\",\"id\":\"1\"}"}) [NameError - undefined local variable or method `current_user' for #<MessageChannel:0x00007fe698e41d68>]: /Users/dannieltung/code/dannieltung/SLACK-GoRails/app/channels/message_channel.rb:4:in `subscribed' | /Users/dannieltung/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/actioncable-6.0.3.7/lib/action_cable/channel/base.rb:181:in `block in subscribe_to_channel' | /Users/dannieltung/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/activesupport-6.0.3.7/lib/active_support/callbacks.rb:112:in `block in run_callbacks' | /Users/dannieltung/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/activesupport-6.0.3.7/lib/active_support/execution_wrapper.rb:84:in `wrap' | /Users/dannieltung/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/actioncable-6.0.3.7/lib/action_cable/engine.rb:68:in `block (3 levels) in <class:Engine>'