avoid concurrenct use of rand.NewSource (#10543)

cmd/object-api-utils.go

@@ -354,12 +354,10 @@ func getHostsSlice(records []dns.SrvRecord) []string {
 	return hosts
 }
 
-var rng = rand.New(rand.NewSource(time.Now().UTC().UnixNano()))
-
 // returns an online host (and corresponding port) from a slice of DNS records
 func getHostFromSrv(records []dns.SrvRecord) (host string) {
 	hosts := getHostsSlice(records)
-
+	rng := rand.New(rand.NewSource(time.Now().UTC().UnixNano()))
 	var d net.Dialer
 	var retry int
 	for retry < len(hosts) {

cmd/test-utils_test.go

@@ -1235,10 +1235,10 @@ func getTestWebRPCResponse(resp *httptest.ResponseRecorder, data interface{}) er
 	return nil
 }
 
-var src = rand.NewSource(UTCNow().UnixNano())
-
 // Function to generate random string for bucket/object names.
 func randString(n int) string {
+	src := rand.NewSource(UTCNow().UnixNano())
+
 	b := make([]byte, n)
 	// A rand.Int63() generates 63 random bits, enough for letterIdxMax letters!
 	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {