由于需要在 Rails 项目中监听 MQTT 所有的事件进行处理，于是在 config/initializers/mqtt.rb 中定义了以下代码，但是总是无法获取到线程中的实例，请教问题在哪？

require 'mqtt'
require 'logger'
require 'mqtt_event_handler'

mqtt_config = Rails.application.config_for(:mqtt).symbolize_keys
mutex = Mutex.new
resource = ConditionVariable.new

Thread.new do
  mutex.synchronize do
    mqtt_config.merge!(client_id: "#{Rails.env.upcase}#{Thread.current.object_id}")
    begin
      @client = MQTT::Client.connect(mqtt_config)
      topics = ['#']
      @client.subscribe(*topics)
      resource.broadcast
      resource.wait(mutex)
      @client.get do |t, m|
        MQTTEventHandler.call(t, m)
      end
    rescue MQTT::ProtocolException => error
      Logger.error error.message
    end
  end
end

thread = Thread.new do
  mutex.synchronize do
    Thread.current[:client] = @client
    puts Thread.current[:client] #> #<MQTT::Client:0x007fda10245e90>
    resource.signal
  end
end

puts thread[:client] #> nil