Add svg generation time

main.go

@@ -45,6 +45,11 @@ var (
 		Name: "badge_requested_total",
 		Help: "The total request number of badges",
 	})
+
+	badgeGenerationTime = promauto.NewHistogram(prometheus.HistogramOpts{
+		Name: "badge_generation_time",
+		Help: "The time consumed for badge generation",
+	})
 )
 
 type Metric struct {
@@ -99,6 +104,8 @@ func main() {
 }
 
 func generateSVG(client api.Client, c *gin.Context) error {
+	startTime := time.Now()
+
 	queryName := c.Param("name")
 	query, ok := queriesMap[queryName]
 	if !ok {
@@ -124,6 +131,7 @@ func generateSVG(client api.Client, c *gin.Context) error {
 	valueText := strconv.Itoa(int(metric.Value))
 	canvas.Text(badgeWidth*0.7, 15, valueText, textStyle)
 	canvas.End()
+	badgeGenerationTime.Observe(float64(time.Now().Sub(startTime).Microseconds()))
 	badgeRequested.Inc()
 
 	return nil