Check if golint exists first in hack/verify-golint.sh

hack/verify-golint.sh

@@ -23,6 +23,12 @@ source "${KUBE_ROOT}/hack/lib/init.sh"
 
 kube::golang::verify_go_version
 
+if ! which golint > /dev/null; then
+  echo 'Can not find golint, install with:'
+  echo 'go get -u github.com/golang/lint/golint'
+  exit 1
+fi
+
 cd "${KUBE_ROOT}"
 
 array_contains () {