is it possible to use koa-passport without session?
Hello, just building a restful api for an ios application, i was trying to use json web token to authenticate all my api end points...

ended up hitting a snag

``` js
// callback version
passport.use(new LocalStrategy({session: false},
  function(username, password, done) {
    pool.getConnection(function(connectionError, connection) {
      console.log('connection error', connectionError);
      const q = {};
      q.sql = 'SELECT ?? FROM ?? WHERE ?? = ?';
      q.values = ['userPwHash', 'user', 'userName', username];
      connection.query(q, function(err, rows) {
        console.log('query error', err);
        console.log('rows', rows);
        if (err) {return done(err); }
        if (!rows.length) {
          return done(null, false, {message: 'Incorrect username.'});
        }
        const dbpwhash = rows[0].userPwHash;
        bcrypt.compare(password, dbpwhash, function(hashError, match) {
          console.log('hasherror', hashError);
          if (match) { return done(null, {userName: username}); }
          if (!match) {return done(null, false, {message: 'Incorrect password.'}); }
        });
        connection.close();
      });
      // pool.end();
    });
  }
));
```

``` bash
Error: Failed to serialize user into session
```

i was wondering if session is required or how i would go about using an auth token for authentication. thanks again!
