Add golang 1.11.x testing (#1514)

* Add golang 1.11.x testing

* remove the latest golang testing

See the issue: https://github.com/gin-gonic/gin/pull/1510

.travis.yml

@@ -6,7 +6,7 @@ go:
   - 1.8.x
   - 1.9.x
   - 1.10.x
-  - master
+  - 1.11.x
 
 git:
   depth: 10