adding linters to travis build

.travis.yml

@@ -8,14 +8,13 @@ go:
 
 go_import_path: gopkg.in/jcmturner/gokrb5.v3
 
-gobuild_args: -tags=integration -race
-
 sudo: required
 
 services:
   - docker
 
 before_install:
+  - go get github.com/golang/lint/golint
   - docker pull jcmturner/gokrb5:http
   - docker pull jcmturner/gokrb5:dns
   - docker pull jcmturner/gokrb5:kdc-centos-default
@@ -35,6 +34,12 @@ before_script:
 env:
   - TEST_KDC_ADDR=127.0.0.1 TEST_HTTP_URL="http://host.test.gokrb5/index.html" DNSUTILS_OVERRIDE_NS="127.0.0.1:53"
 
+script:
+  - test -z $(gofmt -s -l $GO_FILES)         # Fail if a .go file hasn't been formatted with gofmt
+  - go test -v -race -tags=integration ./...                   # Run all the tests with the race detector enabled
+  - go vet ./...                             # go vet is the official Go static analyzer
+  - golint -set_exit_status $(go list ./...) # golint
+
 addons:
   hosts:
     - host.test.gokrb5