Migration umable to be run

20180206211408_create_users.cr

class CreateUsers::V20180206211408 < LuckyMigrator::Migration::V1
  def migrate
    create :users do
      add name : String
      add age : Int32?
    end

    # Run custom SQL with execute
    #
    # execute "CREATE UNIQUE INDEX things_title_index ON things (title);"
  end

  def rollback
    drop :users
  end
end