add redis service

.travis.yml

@@ -7,7 +7,11 @@ env:
 # You don't need to test on very old version of the Go compiler. It's the user's
 # responsibility to keep their compilers up to date.
 go:
-  - 1.11.x
+  - "1.10"
+
+# Setup database services required during tests.
+services:
+  - redis-server
 
 # Only clone the most recent commit.
 git: