How can I get the session value in socket.io

Question

session was store in mongodb. When the user get to the website.But I can't get the session value

var cookieParser=require("cookie-parser");
var signedCookieParser=cookieParser("technode");
var sessionStore=new MongoStore({url:"mongodb://localhost/technode"});

io.set('authorization', function(handshakeData, accept) {
    //console.log(handshakeData.headers);

  signedCookieParser(handshakeData, {}, function(err) {
    if (err) {
      accept(err, false)
    } else {
      sessionStore.get(handshakeData.signedCookies['connect.sid'], function(err, session) {
        if (err) {
          accept(err.message, false)
        } else {
          handshakeData.session = session;
          console.log(handshakeData.session);   //But I can't get the value
          if (session) {
            accept(null, true)
          } else {
            accept('No login')
          }
        }
      })
    }
  })
  accept(null,true);    
})

I want to print the handshakeData.session.But it turn to "undefined"