diff --git a/vendor/github.com/mongodb/mongo-go-driver/x/mongo/driver/session/cluster_clock.go b/vendor/github.com/mongodb/mongo-go-driver/x/mongo/driver/session/cluster_clock.go
new file mode 100644
index 0000000..85376bf
--- /dev/null
+++ b/vendor/github.com/mongodb/mongo-go-driver/x/mongo/driver/session/cluster_clock.go
@@ -0,0 +1,36 @@
+// Copyright (C) MongoDB, Inc. 2017-present.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License. You may obtain
+// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+package session
+
+import (
+	"sync"
+
+	"github.com/mongodb/mongo-go-driver/bson"
+)
+
+// ClusterClock represents a logical clock for keeping track of cluster time.
+type ClusterClock struct {
+	clusterTime bson.Raw
+	lock        sync.Mutex
+}
+
+// GetClusterTime returns the cluster's current time.
+func (cc *ClusterClock) GetClusterTime() bson.Raw {
+	var ct bson.Raw
+	cc.lock.Lock()
+	ct = cc.clusterTime
+	cc.lock.Unlock()
+
+	return ct
+}
+
+// AdvanceClusterTime updates the cluster's current time.
+func (cc *ClusterClock) AdvanceClusterTime(clusterTime bson.Raw) {
+	cc.lock.Lock()
+	cc.clusterTime = MaxClusterTime(cc.clusterTime, clusterTime)
+	cc.lock.Unlock()
+}