travis: build with go1.9.x

Author: spinlock

.travis.yml

@@ -5,6 +5,7 @@ os:
     - osx
 
 go:
+    - 1.9.x
     - 1.8.x
     - 1.7.x
     - 1.6.x
@@ -30,4 +31,4 @@ deploy:
     on:
         repo: CodisLabs/codis
         tags: true
-        condition: $TRAVIS_GO_VERSION =~ ^1\.[7-8]\.[0-9]+$
+        condition: $TRAVIS_GO_VERSION =~ ^1\.[7-9]\.[0-9]+$