Register node module in design time and read data in run-time

Im implementing a node application that have app.js and server.js (using express) . To run my application you should run the server.js which start to listen to http calls. so far so good :).

There is a new requirements like following:

1. Register new module to the application during design time like adding new module to it

2. in Runtime find which modules are register and do my logic on them(the logic is not the point here)

I think its like command design pattern that external module can register to your module and you don't know about them until the need to run

How I can do it in node.js? There is a npm module which allow module registration which I can use as reference ?

I'm not talking about adding a module as node dependency(on package.json), I'm referring that developer will add/register his module to my module by code and in runtime I will know that userModule was register and do additional logic.

require my module myModule.register('userModule');

or register with path to the userModule

myModule.register('/path to user module');