Use timer helper

go/proxyd/server.go

@@ -12,7 +12,6 @@ import (
   "io"
   "io/ioutil"
   "net/http"
-	"time"
 )
 
 var (
@@ -175,9 +174,8 @@ func writeRPCError(w http.ResponseWriter, id *int, code int, msg string) {
 func instrumentedHdlr(h http.Handler) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		httpRequestsCtr.Inc()
-		start := time.Now()
+		timer := prometheus.NewTimer(httpRequestDurationSummary)
+		defer timer.ObserveDuration()
 		h.ServeHTTP(w, r)
-		dur := time.Since(start)
-		httpRequestDurationSummary.Observe(float64(dur) / float64(time.Second))
 	}
 }