migrating dependency management to go.mod, fix shutdown on lease lost

```improvement operator
fix for shutdown on lease lost
```

.ci/check

@@ -40,21 +40,26 @@ ignore=(
    ": exported "
 )
 
-# Install Golint (linting tool).
-go get -u golang.org/x/lint/golint
+# Build Golint.
+go install -mod=vendor ./vendor/golang.org/x/lint/golint
 
 ###############################################################################
 
 join_by() { local IFS="$1"; shift; echo "$*"; }
 
-PACKAGES="$(go list -e ./... | grep -vE '/tmp/|/vendor/|/local/')"
-LINT_FOLDERS="$(echo ${PACKAGES} | sed "s|$GITPROVIDER/$PROJECT|.|g")"
+PACKAGES="$(go list -mod=vendor -e ./... | grep -vE '/tmp/|/vendor/|/local/')"
+PACKAGES_DIRS="$(echo ${PACKAGES} | sed "s|$GITPROVIDER/$PROJECT|.|g")"
 
 # Execute static code checks.
-#go vet ${PACKAGES}
+go vet -mod=vendor ${PACKAGES}
+
+# go fmt ignores -mod=vendor and performs module lookup (https://github.com/golang/go/issues/27841).
+# Also go fmt is just alias for gofmt -l -w and does not support flags that gofmt does.
+# That is why gofmt is used.
 
 # Execute automatic code formatting directive.
-go fmt ${PACKAGES}
+echo "Running gofmt..."
+gofmt -l -w -s ${PACKAGES_DIRS}
 
 # Execute lint checks.
-hack/lint -vacs  ${LINT_FOLDERS}
+hack/lint -vacs  ${PACKAGES_DIRS}

.ci/test

@@ -29,8 +29,7 @@ source "$SOURCE_PATH/build/setupenv.src"
 
 # Install Ginkgo (test framework) to be able to execute the tests.
 echo "Installing Ginkgo..."
-go get -u github.com/onsi/gomega
-go get -u github.com/onsi/ginkgo/ginkgo
+go install -mod=vendor ./vendor/github.com/onsi/ginkgo/ginkgo
 
 ###############################################################################
 
@@ -40,4 +39,4 @@ if [[ ! -z "$COVERAGE" ]]; then
 fi
 
 echo "Running tests..."
-ginkgo ${COVER_FLAG} -r cmd pkg plugin
+GOFLAGS="-mod=vendor" ginkgo ${COVER_FLAG} -r cmd pkg plugin

Makefile

@@ -2,32 +2,48 @@ EXECUTABLE=dns-controller-manager
 PROJECT=github.com/gardener/external-dns-management
 VERSION=$(shell cat VERSION)
 
+.PHONY: revendor
+revendor:
+	@GO111MODULE=on go mod vendor
+	@GO111MODULE=on go mod tidy
 
-.PHONY: build local-build release test alltests
 
+.PHONY: check
+check:
+	@.ci/check
 
+.PHONY: build
 build:
-	GOOS=linux GOARCH=amd64 go build -o $(EXECUTABLE) \
+    @CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GO111MODULE=on go build -o $(EXECUTABLE) \
+        -mod=vendor \
 	    -ldflags "-X main.Version=$(VERSION)-$(shell git rev-parse HEAD)"\
 	    ./cmd/dns
 
-build-local: local-build
-
-local-build:
-	go build -o $(EXECUTABLE) \
+.PHONY: build-local
+build-local:
+	@CGO_ENABLED=0 GO111MODULE=on go build -o $(EXECUTABLE) \
+	    -mod=vendor \
 	    -ldflags "-X main.Version=$(VERSION)-$(shell git rev-parse HEAD)"\
 	    ./cmd/dns
 
+.PHONY: release
 release:
-	GOOS=linux GOARCH=amd64 go build -o $(EXECUTABLE) \
+	@CGO_ENABLED=0 GOOS=linux GOARCH=amd64 GO111MODULE=on go build -o $(EXECUTABLE) \
+	    -a \
+	    -mod=vendor \
 	    -ldflags "-X main.Version=$(VERSION) \
 	    ./cmd/dns
 
+.PHONY: test
 test:
-	go test ./pkg/...
+	GO111MODULE=on go test -mod=vendor ./pkg/...
 	@echo ----- Skipping long running integration tests, use \'make alltests\' to run all tests -----
 	test/integration/run.sh $(kindargs) -- -skip Many $(args)
 
+.PHONY: generate
+generate:
+	@./hack/generate-code
+
 alltests:
-	go test ./pkg/...
+	GO111MODULE=on go test -mod=vendor ./pkg/...
 	test/integration/run.sh $(kindargs) -- $(args)

go.mod

@@ -0,0 +1,42 @@
+module github.com/gardener/external-dns-management
+
+go 1.13
+
+require (
+	github.com/Azure/azure-sdk-for-go v39.0.0+incompatible
+	github.com/Azure/go-autorest/autorest/azure/auth v0.4.2
+	github.com/Azure/go-autorest/autorest/to v0.3.0 // indirect
+	github.com/Masterminds/semver v1.4.2 // indirect
+	github.com/ahmetb/gen-crd-api-reference-docs v0.1.5
+	github.com/aliyun/alibaba-cloud-sdk-go v0.0.0-20190603021944-12ad9f921c0b
+	github.com/aws/aws-sdk-go v1.19.41
+	github.com/emicklei/go-restful v2.9.6+incompatible // indirect
+	github.com/gardener/controller-manager-library v0.1.1-0.20200204110458-c263b9bb97ad
+	github.com/go-openapi/swag v0.19.4 // indirect
+	github.com/golang/groupcache v0.0.0-20190129154638-5b532d6fd5ef // indirect
+	github.com/googleapis/gnostic v0.2.0 // indirect
+	github.com/gophercloud/gophercloud v0.2.0
+	github.com/gophercloud/utils v0.0.0-20190527093828-25f1b77b8c03
+	github.com/imdario/mergo v0.3.7 // indirect
+	github.com/mailru/easyjson v0.0.0-20190626092158-b2ccc519800e // indirect
+	github.com/miekg/dns v1.1.14
+	github.com/onsi/ginkgo v1.10.1
+	github.com/onsi/gomega v1.7.0
+	github.com/prometheus/client_golang v0.9.2
+	github.com/prometheus/client_model v0.0.0-20190129233127-fd36f4220a90 // indirect
+	github.com/prometheus/common v0.2.0 // indirect
+	github.com/prometheus/procfs v0.0.0-20190328153300-af7bedc223fb // indirect
+	golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3
+	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45
+	golang.org/x/tools v0.0.0-20190715044752-607ca053a137 // indirect
+	google.golang.org/api v0.4.0
+	k8s.io/api v0.16.4
+	k8s.io/apiextensions-apiserver v0.16.4
+	k8s.io/apimachinery v0.17.0
+	k8s.io/client-go v0.16.4
+	k8s.io/code-generator v0.16.4
+	k8s.io/kube-openapi v0.0.0-20191107075043-30be4d16710a
+	sigs.k8s.io/kind v0.7.0
+)
+
+replace gopkg.in/fsnotify.v1 v1.4.7 => github.com/fsnotify/fsnotify v1.4.7