app-init.js

var mongoose = require('mongoose')
, testClient = require('api_client')   // npm link'd 
;

mongoose.connect('localhost', 'delete-me');

testClient.getItems({name: 'foo'})
  .then(function(){
    console.log(item);
  });

module-index.js

/* export a function that accepts mongoose conx
   and use it to initialize the module 
*/
exports = module.exports = function (mongoose) {
	return new FooService(mongoose)
}

// use the mongoose instance to create model
function FooService(mongoose) {
	this.model = require('./bar.model.js')(mongoose)
}

FooService.prototype.getItems = function getItems (query) {
	return this.model.findAsync(query)
}

module-model.js

var Promise = require('bluebird')

/*  export a function which accepts a mongoose instance, 
 *  creates a model on it, and returns the model
 */
exports = module.exports = function genModel(mongoose) {

	var BarSchema = new mongoose.Schema({
		name: 	{ type: String},
		age: 	{ type: Number, default: 0}
	})

	mongoose.model('Bar', BarSchema)
	return Promise.promisifyAll(mongoose.model('Bar'))

}