chore(ci): add go 1.9 version (#1082)

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

.travis.yml

@@ -4,6 +4,7 @@ go:
   - 1.6.x
   - 1.7.x
   - 1.8.x
+  - 1.9.x
   - master
 
 git: