Call method of a Ruby Singleton without instance

base.rb

require 'singleton'
require 'forwardable'

class Postman
  include Singleton
  
  class << self
    extend Forwardable
    
    def_delegators :instance, :post, :delete
  end
  
  def post
    puts 'post!'
  end
  
  def delete
    puts 'delete!'
  end
end

Postman.post    #=> 'post!'
Postman.delete  #=> 'delete!'

base_on_rails.rb

require 'singleton'

class Postman
  include Singleton
  
  class << self
    delegate :post, :delete, to: :instance
  end
  
  def post
    puts 'post!'
  end
  
  def delete
    puts 'delete!'
  end
end

Postman.post    #=> 'post!'
Postman.delete  #=> 'delete!'