Revert "rollback appveyor to use 1.10.4"

This reverts commit 0c8551ea6beaa4e8166836d5a4e96a50a4ce48a8.

appveyor.yml

@@ -13,7 +13,7 @@ version: "1.0.{build}"
 environment:
   global:
     GOPATH: C:\gopath
-    GOVERSION: "1.10.4"
+    GOVERSION: "1.11"
 
 install:
   - set PATH=%GOPATH%\bin;c:\go\bin;%PATH%