You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: configuration.rb
    path of file: ./repos/gush/lib/gush
    
    the code of the file until where you have to start completion: module Gush
  class Configuration
    attr_accessor :concurrency, :namespace, :redis_url, :ttl, :locking_duration, :polling_interval

    def self.from_json(json)
      new(Gush::JSON.decode(json, symbolize_keys: true))
    end

    def initialize(hash = {})
      self.concurrency      = has
    
    def initialize(hash = {})
      self.concurrency      = hash.fetch(:concurrency, 5)
      self.namespace        = hash.fetch(:namespace, 'gush')
      self.redis_url        = hash.fetch(:redis_url, 'redis://localhost:6379')
      self.gushfile         = hash.fetch(:gushfile, 'Gushfile')
      self.ttl              = hash.fetch(:ttl, -1)
      self.locking_duration = hash.fetch(:locking_duration, 2) # how long you want to wait for the lock to be released, in seconds
      self.polling_interval = hash.fetch(:polling_internal, 0.3) # how long the polling interval should be, in seconds
    end