Run $ /node_modules/.bin/sequelize migration:generate --name 1m_user_to_dids

sequelize-migration-addColumn.js

'use strict';

module.exports = {
  up: (queryInterface, Sequelize) => {
    return queryInterface.addColumn(
      'Dids', 
      'UserId', 
      {
        type: Sequelize.INTEGER,
        references: { 
          model: 'Users', 
          key: "id" 
        },
        onDelete: 'cascade',
        allowNull: false
      })
  },

  down: (queryInterface, Sequelize) => {
    return queryInterface.removeColumn('Dids', 'UserId');
  }
};