Add go 1.12 to Travis-CI

Since `go tool vet` is deprecated in Go 1.12, add a hack/verify-govet.sh
script that behaves differently for Go 1.{9,10,11}, with the default
behavior supporting the new `go vet` for 1.12+.

Author: codenrhoden

.travis.yml

@@ -4,6 +4,7 @@ go:
   - 1.9.x
   - 1.10.x
   - 1.11.x
+  - 1.12.x
 go_import_path: k8s.io/utils
 script:
   - make verify

Makefile

@@ -30,7 +30,7 @@ verify-lint:
 
 .PHONY: vet
 vet:
-	go tool vet .
+	./hack/verify-govet.sh
 
 .PHONY: update-fmt
 update-fmt:

hack/verify-govet.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+
+# Copyright 2019 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# For use with Go 1.12+
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+GO_VERSION=${TRAVIS_GO_VERSION:-$(go version | cut -d ' ' -f 3)}
+
+if [[ ${GO_VERSION} =~ ^(go)?1\.(9|10|11) ]]; then
+    go tool vet .
+else
+  go vet ./...
+fi