Properly close mongoose's connection once you're done

I'm using mongoose in a script that is not meant to run continuously, and I'm facing what seems to be a very simple issue yet I can't find an answer; simply put once I make a call to any mongoose function that sends requests to mongodb my nodejs instance never stops and I have to kill it manually with, say, Ctrl+c or Program.exit().

The code looks roughly like this:
var mongoose = require('mongoose'); 
// if my program ends after this line, it shuts down as expected, my guess is that the connection is not really done here but only on the first real request ? 
mongoose.connect('mongodb://localhost:27017/somedb'); 
// define some models 
// if I include this line for example, node never stop afterwards 
var MyModel = mongoose.model('MyModel', MySchema);

I tried adding calls to mongoose.disconnect() but no to result. Aside from that, everything works fine (finding, saving, ...). Don’t know  how mongoose close connection?