diff --git a/vendor/github.com/google/btree/btree.go b/vendor/github.com/google/btree/btree.go
index 6ff062f..b83acdb 100644
--- a/vendor/github.com/google/btree/btree.go
+++ b/vendor/github.com/google/btree/btree.go
@@ -796,7 +796,7 @@
 }
 
 // DescendGreaterThan calls the iterator for every value in the tree within
-// the range (pivot, last], until iterator returns false.
+// the range [last, pivot), until iterator returns false.
 func (t *BTree) DescendGreaterThan(pivot Item, iterator ItemIterator) {
 	if t.root == nil {
 		return
diff --git a/vendor/github.com/google/btree/go.mod b/vendor/github.com/google/btree/go.mod
new file mode 100644
index 0000000..fe4d5ca
--- /dev/null
+++ b/vendor/github.com/google/btree/go.mod
@@ -0,0 +1,17 @@
+// Copyright 2014 Google Inc.
+//
+// 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
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+module github.com/google/btree
+
+go 1.12