add jitter (#1298)

util/jitter/jitter.go

@@ -0,0 +1,17 @@
+// Package jitter provides a random jitter
+package jitter
+
+import (
+	"math/rand"
+	"time"
+)
+
+var (
+	r = rand.New(rand.NewSource(time.Now().UnixNano()))
+)
+
+// Do returns a random time to jitter with max cap specified
+func Do(d time.Duration) time.Duration {
+	v := r.Float64() * float64(d.Nanoseconds())
+	return time.Duration(v)
+}