How to add foreign key in sequelize cockroachdb

I have model like
```
let init = function() {
return user_management = connection.define('user_management', {
id: {
type: DataTypes.INTEGER,
primaryKey: true,
autoIncrement: true
},
email_id: {
type: sequelize.STRING,
allowNull: false
},
password: {
type: sequelize.STRING
},
first_name: {
type: sequelize.STRING,
allowNull: false
},
middle_name: {
type: sequelize.STRING,
allowNull: true
},
last_name: {
type: sequelize.STRING,
allowNull: false
},
title: {
type: sequelize.STRING,
allowNull: false
},
company_name: {
type: sequelize.STRING,
allowNull: true
},
organisation_strength: {
type: sequelize.STRING,
allowNull: true
},
industry: {
type: sequelize.STRING,
allowNull: true
},
phone_number: {
type: sequelize.INTEGER,
allowNull: false
},
url: {
type: sequelize.STRING,
allowNull: true
},
personnel_number: {
type: sequelize.INTEGER,
allowNull: true
},
},
// I want to add unit id as foreign key in usermanagement table.
classMethods: {
associate: function(model) {
var usermanagement = model.user_management;
var unit = model.unit;
usermanagement.belongsTo(unit)
},
})
}
module.exports = init
```

I am getting error while trying to create table
Unhandled rejection SequelizeDatabaseError: unimplemented at or near "null"
**CREATE TABLE IF NOT EXISTS "user_managements" ("id" SERIAL , "email_id" VARCHAR(255) NOT NULL, "password" VARCHAR(255), "first_name" VARCHAR(255) NOT NULL, "middle_name" VARCHAR(255), "last_name" VARCHAR(255) NOT NULL, "title" VARCHAR(255) NOT NULL, "company_name" VARCHAR(255), "organisation_strength" VARCHAR(255), "industry" VARCHAR(255), "phone_number" INTEGER NOT NULL, "url" VARCHAR(255), "personnel_number" INTEGER, "user_role" VARCHAR(255) NOT NULL, "salt" VARCHAR(255), "createdAt" TIMESTAMP WITH TIME ZONE NOT NULL, "updatedAt" TIMESTAMP WITH TIME ZONE NOT NULL, "unitId" INTEGER REFERENCES "units" ("id") ON DELETE SET NULL ON UPDATE CASCADE, PRIMARY KEY ("id"));**