gopls: update go.mod file for pre-release

Change-Id: I23176dd86f259e58f5902f4cc097ef463ba336c4
Reviewed-on: https://go-review.googlesource.com/c/tools/+/216720
Reviewed-by: Robert Findley <rfindley@google.com>
diff --git a/gopls/go.mod b/gopls/go.mod
index afdeb65..45e789b 100644
--- a/gopls/go.mod
+++ b/gopls/go.mod
@@ -5,7 +5,7 @@
 require (
 	github.com/sergi/go-diff v1.0.0
 	github.com/stretchr/testify v1.4.0 // indirect
-	golang.org/x/tools v0.0.0-20191017151554-a3bc800455d5
+	golang.org/x/tools v0.0.0-20200128221035-c00a2daf0567
 	honnef.co/go/tools v0.0.1-2019.2.3
 	mvdan.cc/xurls/v2 v2.1.0
 )