问题 Rails 5 actioncable undefined方法`fetch'代表nil：NilClass

我正在使用Rails 5 actioncable 而我正在接受 这个错误 当尝试发送任何抛出的东西 actioncable 我该怎么办？ 我正在尝试将项目推向Heroku。

NoMethodError in MessagesController#create

undefined method `fetch' for nil:NilClass
Extracted source (around line #37):

#35       # Also makes sure proper dependencies are required.
#36       def pubsub_adapter
*37         adapter = (cable.fetch('adapter') { 'redis' })
#38         path_to_adapter = "action_cable/subscription_adapter/#{adapter}"
#39         begin
#40           require path_to_adapter

Extracted source (around line #50):

#48       # Adapter used for all streams/broadcasting.
#49       def pubsub
*50         @pubsub ||= config.pubsub_adapter.new(self)
#51       end
#52 
#53       # All the identifiers applied to the connection class associated with this server.

Extracted source (around line #42):

#40           def broadcast(message)
#41             server.logger.info "[ActionCable] Broadcasting to #{broadcasting}: #{message}"
*42             server.pubsub.broadcast broadcasting, ActiveSupport::JSON.encode(message)
#43           end
#44         end
#45     end


Rails.root: /media/adham/Data/code/rails5test

Application Trace
app/controllers/messages_controller.rb:6:in `create'
app/middleware/chat_action_cable.rb:10:in `call'