Merge pull request #630 from kinvolk/dongsu/fix-golint-fetch

travis: fix fetch issue of golint

Author: Zhou Hao

.travis.yml

@@ -7,7 +7,9 @@ go:
 sudo: false
 
 before_install:
-  - go get github.com/golang/lint/golint
+  - mkdir --parents $GOPATH/src/golang.org/x
+    && git clone --depth=1 https://go.googlesource.com/lint $GOPATH/src/golang.org/x/lint
+    && go get golang.org/x/lint/golint
   - go get github.com/vbatts/git-validation
 
 install: true