module MyApp
  module JobHelpers
    before_perform do |job|
      # stuff to do
    end
  end
end

require 'my_app/job_helpers'

class TheJob < ActiveJob::Base
  include MyApp::JobHelpers

 # Do more stuff
end

module MyApp
  module JobHelpers
    extend ActiveSupport::Concern

    included do

      # inside this you can call ActiveJob helpers
      before_perform do
        # stuff to do
      end
    end
  end
end

module MyApp
  module JobHelpers
    def self.included(job_class)
      job_class.before_perform do |job|
        # work to be completed
      end
    end
  end
end