code: func (agent *Agent) WrapHTTPHandlerFunc(h tHTTPHandlerFunc) tHTTPHandlerFunc {
  	agent.CollectHTTPStat = true
  	agent.initTimer()
  	return func(w http.ResponseWriter, req *http.Request) {
  		proxy := newHTTPHandlerFunc(h)
  		proxy.timer = agent.HTTPTimer
  		//set the http status counters before serving request.
  		proxy.httpStatusCounters = agent.HTTPStatusCounters
  		proxy.ServeHTTP(w, req)
  	}
  }
docs: //WrapHTTPHandlerFunc  instrument HTTP handler functions to collect HTTP metrics