chore: add go v2 init template (#14785)

Adds go `app` init template for cdk v2. References aws-cdk-go v2
and constructs v10.

Testing: Checked out the v2-main branch and added this init template to
the CLI. Changed the version of `packages/aws-cdk/package.json` from
`0.0.0` to `2.0.0-rc.4` and ran `buildup`. Then ran `cdk init
--language=go` against local build of CLI and verified that `cdk ls` and
`cdk synth` both output correctly using both local cli and `npx
cdk@next`.


----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/aws-cdk/lib/init-templates/v2/app/go/%name%.template.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"github.com/aws/aws-cdk-go/awscdk/v2"
+	"github.com/aws/aws-cdk-go/awscdk/v2/awssns"
+	"github.com/aws/constructs-go/constructs/v10"
+	"github.com/aws/jsii-runtime-go"
+)
+
+type %name.PascalCased%StackProps struct {
+	awscdk.StackProps
+}
+
+func New%name.PascalCased%Stack(scope constructs.Construct, id string, props *%name.PascalCased%StackProps) awscdk.Stack {
+	var sprops awscdk.StackProps
+	if props != nil {
+		sprops = props.StackProps
+	}
+	stack := awscdk.NewStack(scope, &id, &sprops)
+
+	// The code that defines your stack goes here
+
+	// as an example, here's how you would define an AWS SNS topic:
+	awssns.NewTopic(stack, jsii.String("MyTopic"), &awssns.TopicProps{
+		DisplayName: jsii.String("MyCoolTopic"),
+	})
+
+	return stack
+}
+
+func main() {
+	app := awscdk.NewApp(nil)
+
+	New%name.PascalCased%Stack(app, "%name.PascalCased%Stack", &%name.PascalCased%StackProps{
+		awscdk.StackProps{
+			Env: env(),
+		},
+	})
+
+	app.Synth(nil)
+}
+
+// env determines the AWS environment (account+region) in which our stack is to
+// be deployed. For more information see: https://docs.aws.amazon.com/cdk/latest/guide/environments.html
+func env() *awscdk.Environment {
+	// If unspecified, this stack will be "environment-agnostic".
+	// Account/Region-dependent features and context lookups will not work, but a
+	// single synthesized template can be deployed anywhere.
+	//---------------------------------------------------------------------------
+	return nil
+
+	// Uncomment if you know exactly what account and region you want to deploy
+	// the stack to. This is the recommendation for production stacks.
+	//---------------------------------------------------------------------------
+	// return &awscdk.Environment{
+	//  Account: jsii.String("123456789012"),
+	//  Region:  jsii.String("us-east-1"),
+	// }
+
+	// Uncomment to specialize this stack for the AWS Account and Region that are
+	// implied by the current CLI configuration. This is recommended for dev
+	// stacks.
+	//---------------------------------------------------------------------------
+	// return &awscdk.Environment{
+	//  Account: jsii.String(os.Getenv("CDK_DEFAULT_ACCOUNT")),
+	//  Region:  jsii.String(os.Getenv("CDK_DEFAULT_REGION")),
+	// }
+}

packages/aws-cdk/lib/init-templates/v2/app/go/%name%_test.template.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/aws/aws-cdk-go/awscdk/v2"
+	"github.com/stretchr/testify/assert"
+	"github.com/tidwall/gjson"
+)
+
+func Test%name.PascalCased%Stack(t *testing.T) {
+	// GIVEN
+	app := awscdk.NewApp(nil)
+
+	// WHEN
+	stack := New%name.PascalCased%Stack(app, "MyStack", nil)
+
+	// THEN
+	bytes, err := json.Marshal(app.Synth(nil).GetStackArtifact(stack.ArtifactId()).Template())
+	if err != nil {
+		t.Error(err)
+	}
+
+	template := gjson.ParseBytes(bytes)
+	displayName := template.Get("Resources.MyTopic86869434.Properties.DisplayName").String()
+	assert.Equal(t, "MyCoolTopic", displayName)
+}

packages/aws-cdk/lib/init-templates/v2/app/go/.template.gitignore

@@ -0,0 +1,19 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# go.sum should be committed
+!go.sum
+
+# CDK asset staging directory
+.cdk.staging
+cdk.out

packages/aws-cdk/lib/init-templates/v2/app/go/README.md

@@ -0,0 +1,14 @@
+# Welcome to your CDK Go project!
+
+This is a blank project for Go development with CDK.
+
+**NOTICE**: Go support is still in Developer Preview. This implies that APIs may
+change while we address early feedback from the community. We would love to hear
+about your experience through GitHub issues.
+
+## Useful commands
+
+ * `cdk deploy`      deploy this stack to your default AWS account/region
+ * `cdk diff`        compare deployed stack with current state
+ * `cdk synth`       emits the synthesized CloudFormation template
+ * `go test`         run unit tests

packages/aws-cdk/lib/init-templates/v2/app/go/cdk.template.json

@@ -0,0 +1,3 @@
+{
+  "app": "go mod download && go run %name%.go"
+}

packages/aws-cdk/lib/init-templates/v2/app/go/go.template.mod

@@ -0,0 +1,13 @@
+module %name%
+
+go 1.16
+
+require (
+  github.com/aws/aws-cdk-go/awscdk/v2 v%cdk-version%
+  github.com/aws/constructs-go/constructs/v10 v10.0.5
+  github.com/aws/jsii-runtime-go v1.29.0
+
+  // for testing
+  github.com/tidwall/gjson v1.7.4
+  github.com/stretchr/testify v1.7.0
+)