Can't use a different configuration

[diegoponciano]

I'm trying to use this lib in a project (ruby 2.3.1p112 and 'rails', '~> 5.0.1'), but wasn't able to point to a different YAML configuration. I've put the following code into config/initializers/cnab150.rb:

Cnab150.configure do |config|
  config.layout_file_path = "#{Rails.root}/config/cnab150.yml"
end

But I get this: project/config/initializers/cnab150.rb:2:in `block in <top (required)>': undefined method `layout_file_path=' for nil:NilClass (NoMethodError)

[ghost]

To follow up, I monkeypatched the configuration file and it worked. I'm very new to ruby/rails, so I'm not really sure what's going on, but I guess it's got to do with the Rails version I'm using.
Code patched:

module Cnab150
  class << self
    attr_accessor :config
  end

  def self.configure
    self.config ||= Configuration.new
    yield(config)
  end

  class Configuration
    attr_accessor :layout_file_path

    def initialize
      @layout_file_path = "#{File.dirname(__dir__)}/../config/layout.yml"
    end

    # The layouts method load the layouts from the yml file.
    def layouts
      @_ ||= YAML.load_file(@layout_file_path)['cnab150']
    end
  end
end