Upgrade golang-protobuf to v1.3.5

Test: None
Change-Id: I7b882d48107b84828cc122f40017728abf86477e
diff --git a/METADATA b/METADATA
index e4adcf7..cfd2016 100644
--- a/METADATA
+++ b/METADATA
@@ -8,10 +8,10 @@
     type: GIT
     value: "https://github.com/golang/protobuf"
   }
-  version: "v1.3.4"
+  version: "v1.3.5"
   last_upgrade_date {
     year: 2020
-    month: 2
-    day: 26
+    month: 3
+    day: 12
   }
 }
diff --git a/go.mod b/go.mod
index de28f6f..aa05582 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/golang/protobuf
 
-go 1.12
+go 1.9