ci: update to xenial

sbinet · sbinet · commit cdd7d6868d69 · 2019-04-08T20:43:01.000+02:00
Migrate to xenial to workaround golang/go#31293
diff --git a/.travis.yml b/.travis.yml
@@ -1,3 +1,5 @@
+dist: xenial
+
 language: go
 go_import_path: go-hep.org/x/hep
 os:
