Knex:Error Pool2 - Error: Error allocating resources: connect ECONNREFUSED

I'm using bookshelf.js on a node.js project and it works fine on my localhost. But when I tried to put it on AWS + RDS, it gives me the following error:

Express server listening on port 8000
Knex:Error Pool2 - Error: Error allocating resources: connect ECONNREFUSED
Knex:Error Pool2 - Error: Error allocating resources: connect ECONNREFUSED

Obviously my connection configs were changed.

module.exports = {
      host     : 'https://my_rds_url:3306',
      user     : 'root',
      database     : 'my_database',
      password : 'my_pw'
}

What could it be?

Thanks.