re.params，从Node js中的外部函数获取（名称或值）？

Question

如何获取req.params值或名称来访问它？

我需要类似req.params = {track:'somevalue'}或{id: 123} ....

app.use(function(req, res, next){
  if(req.method == 'GET'){
    var data = req.params; //params is undefined    
  }
})

app.get('/info/:track', (req, res) => {})
app.get('/profile/:id', (req, res) => {})
app.get('/courses/:session', (req, res) => {})
app.get('/somethingelse/:last', (req, res) => {})