db-config.rb

module MyGem
  class DbConfig
    CONFIGURATIONS = Psych.safe_load(
      ERB.new(
        File.read(File.join(File.dirname(__FILE__), '../../config/databases.yml'))
      ).result,
      aliases: true
    )

    DB_ENV = (Rails.env if defined?(Rails)) || ENV['RAILS_ENV'] || ENV['RACK_ENV'] || 'development'

    class << self
      def configurations
        CONFIGURATIONS[DB_ENV.to_s]
      end

      def db_key
        RequestStore.store[:mygem_database_key]
      end
    end
  end
end