gopls: update go.mod file for gopls/v0.3.4

Change-Id: Ia76ff9a13704041338368c8b8a812c12f98de719
Reviewed-on: https://go-review.googlesource.com/c/tools/+/223717
Reviewed-by: Heschi Kreinick <heschi@google.com>
diff --git a/gopls/go.mod b/gopls/go.mod
index c551e79..301494a 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 v0.0.0-20200227200655-6862ededa516
+	golang.org/x/tools v0.0.0-20200316194252-fafb6e2e8a4a
 	honnef.co/go/tools v0.0.1-2020.1.3
 	mvdan.cc/xurls/v2 v2.1.0
 )