chore: update golang version

vendor/github.com/spf13/cobra/.travis.yml

@@ -0,0 +1,29 @@
+language: go
+
+stages:
+  - diff
+  - test
+  - build
+
+go:
+  - 1.12.x
+  - 1.13.x
+  - tip
+
+before_install:
+  - go get -u github.com/kyoh86/richgo
+  - go get -u github.com/mitchellh/gox
+
+matrix:
+  allow_failures:
+    - go: tip
+  include:
+    - stage: diff
+      go: 1.13.x
+      script: make fmt
+    - stage: build
+      go: 1.13.x
+      script: make cobra_generator
+
+script: 
+ - make test