Cache go dependencies in Travis

DirectXMan12 · DirectXMan12 · commit 705565475cb8 · 2019-05-14T15:41:35.000-07:00
This caches the go build cache and go module cache in Travis for faster
builds.
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,10 @@
 language: go
 
+cache:
+  directories:
+  - $HOME/.cache/go-build
+  - $GOPATH/pkg/mod
+
 os:
   - linux
   - osx
