Projekt Tasks: 
Simple and lightweight Koa middleware to handle multilevel and wildcard subdomains
npm install koa-sub-domain
var koa = require('koa');
var app = koa();
var subdomain = require('koa-sub-domain');
app.use(subdomain('sub',function *(next){
this.body = 'Hey, you got it :-)';
}));
app.listen(3000);
In the case you are running multiple domains on this server, you can add FQDN instead of only sub. Also you may user Koa-router routes same as generator functions as target of a domain.
app.use(subdomain('sub.example.com', exampleRoute)); // not exampleRoute.routes() !!!
app.use(subdomain('sub.foobar.com', function*(next){...}));
Also wildcards for the last sub domain are handled same as deeper domains below the *
app.use(subdomain('*.example.com',wildcardRoute));
So intranet.management.example.com is matched by *.example.com
Of cause you can handle multilevel subdomains in chain:
app.use(subdomain('api', router));
app.use(subdomain('v1.api', router));
app.use(subdomain('*.v1.api', router));
Note: The order of chaining is important !
You need a DNS server or you can add all the FQDNs into your /etc/hosts (if you are using Linux or Mac OS X). On Windows 7 and 8, the hosts file path is %systemroot%\system32\drivers\etc.
172.0.0.1 example.com
172.0.0.1 sub.example.com
172.0.0.1 sub.foo.bar.example.com
172.0.0.1 wildcard.sub.foo.bar.example.com
An other way would be to use dnsmasq. You need simple one line in the dnsmasq.conf:
address=/.example.com/192.168.0.1
Note: the . before example.com - this means all requests to sub-domains are landing on 192.168.0.1.
You can optimize performance by knowing the steps Koa-sub-domain is resolving:
sub === this.hostnamethis.subdomain[0] === subtypeof this.subdomain[1] === 'string'// or wildcard => sub sub domain ?
That means FQDNs should be resolved the fastest.
MIT
Note: If you are working for a big company please notice my works as I would be an external - small companies please donate by project success. Open Source contributors: I do not expext something - I love to give you something back !! ###Notes TODO: checking out whether yield has to be replaced by return because of there is no more following match !