class.rb

$LOAD_PATH << '.' 
require 'yaml'
require 'rubygems'
require 'mysql2'
require 'pry-byebug'
require 'creatDatabase'

#binding.pry
class StreamMysql
 include Sgbd
 def mysql_connection(conf)
        @connexion = Mysql2::Client.new(:host => conf['ost'], :username => conf['user'], :password => conf['password'], :table => conf['table'], :port => conf['port'])
        if @connexion
      
         puts check_table_exists
         @connexion.check_table_exists

         puts "connexion etablie"
        
        else
         puts "error connexion"
         end


        rescue Mysql2::Error => e
          puts e.errno
          puts e.error
        @connexion.close
end

 def read_config_file
        config = YAML::load_file(File.join(__dir__, 'config.yml'))
        conf   = config['database']
        mysql_connection(conf)
 end


end 

error.txt

SHOW TABLES;
./yamlReadFile.rb:44:in `mysql_connection': undefined method `check_table_exists' for #<Mysql2::Client:0x000000033a7750> (NoMethodError)

module.rb

module Sgbd

# class ModuleCreateDatabase

  def  create_database

  end

  def check_table_exists
      query=("SHOW TABLES;")
  end

 end