koa session does not work when used in a middleware app

I am using the vhost middleware with koa-session. Since koa-session 2.0.0 is was possible to use it in a subapp. Since 3.0.0 this does not work anymore. Example:

var session = require('./');
var koa = require('koa');
var compose = require('koa-compose');
var app = koa();

app.keys = ['some secret hurr'];

app.use(session(app));

app.use(function* (next){
  if ('/favicon.ico' == this.path) return;
  var n = this.session.views || 0;
  this.session.views = ++n;
  this.body = n + ' views';
});

var server = koa();
server.use(compose(app.middleware));
server.listen(3000);

console.log('listening on port 3000');

[chrisveness]

I don’t recall any longer what the issue turned out to be, but I am successfully using koa-session on a per-app basis with Koa v2: e.g. https://github.com/chrisveness/koa-sample-web-app-api-mysql/blob/master/app.js (don’t know about a ‘recommended’ solution!).

Things are a bit more complex if you want to have session variables common to multiple sub-apps: you would have to use the domain option, setting it to the super-domain common to your sub-domains. Bear in mind, though, that for testing, cookies on localhost can be problematic.

[chrisveness]

I am also having problems with koa-session (in fact, koa-flash) which I suspect may be related to this.

I am using virtual host apps as per https://github.com/koajs/examples/tree/master/vhost.

Is it possible to use koa-session with this configuration? If so, could you give me a pointer as to how it should be done? If not, have you any other suggestions?

Thanks.