Error handling. Vendoring

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

vendor/github.com/go-redis/redis/internal/internal.go

@@ -0,0 +1,24 @@
+package internal
+
+import (
+	"math/rand"
+	"time"
+)
+
+// Retry backoff with jitter sleep to prevent overloaded conditions during intervals
+// https://www.awsarchitectureblog.com/2015/03/backoff.html
+func RetryBackoff(retry int, minBackoff, maxBackoff time.Duration) time.Duration {
+	if retry < 0 {
+		retry = 0
+	}
+
+	backoff := minBackoff << uint(retry)
+	if backoff > maxBackoff || backoff < minBackoff {
+		backoff = maxBackoff
+	}
+
+	if backoff == 0 {
+		return 0
+	}
+	return time.Duration(rand.Int63n(int64(backoff)))
+}