Bump up go version to 1.13.14 for travis (#138)

diff --git a/.travis.yml b/.travis.yml
index bbe821b..370b900 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -21,7 +21,7 @@
     include:
         - os: linux
           sudo: required
-          go: "1.9.3"
+          go: "1.13.14"
           services: docker
           dist: xenial