You can choose any node module you would like to use. The 'http' and
'https' built in modules in node have basic network fetching
functionality. If you want to see an example, the "net" module used
internally in volo is one:
https://github.com/volojs/volo/blob/master/lib/net.js
For modules that are not build into node, you can put some npm
dependencies in the package.json for the template, volo create will
fetch them, and then you can just require() them as you would any node
module in the volofile.
James