install goimports as a tool

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.6.2
 	golang.org/x/crypto v0.0.0-20200302210943-78000ba7a073
+	golang.org/x/tools v0.0.0-20200329025819-fd4102a86c65
 	gotest.tools v2.2.0+incompatible
 	k8s.io/api v0.17.6
 	k8s.io/apimachinery v0.17.6

hack/tools.go

@@ -0,0 +1,23 @@
+// +build tools
+
+/*
+Copyright 2020 The Knative 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.
+*/
+
+package tools
+
+import (
+	// verify codegen
+	_ "golang.org/x/tools/cmd/goimports"
+)