Update the Travis go version

rifelpet · rifelpet · commit d90c3404bedc · 2019-09-13T14:47:31.000-07:00
This matches what the other prow jobs use
diff --git a/.travis.yml b/.travis.yml
@@ -7,7 +7,7 @@ env:
     - GO111MODULE=on
 
 go:
-  - "1.11.2"
+  - "1.12.9"
 
 cache:
   directories:
