+++
title = "Use the hit counter"
weight = 400
+++

## Add a hit counter to our stack

Okay, our hit counter is ready. Let's use it in our app. Open `cdk-workshop.go` and add
the following highlighted code:

{{<highlight go "hl_lines=4 30-32 35">}}
package main

import (
	"cdk-workshop/hitcounter"

	"github.com/aws/aws-cdk-go/awscdk/v2"
	"github.com/aws/aws-cdk-go/awscdk/v2/awslambda"
	"github.com/aws/aws-cdk-go/awscdk/v2/awsapigateway"
	"github.com/aws/constructs-go/constructs/v10"
	"github.com/aws/jsii-runtime-go"
)

type CdkWorkshopStackProps struct {
	awscdk.StackProps
}

func NewCdkWorkshopStack(scope constructs.Construct, id string, props *CdkWorkshopStackProps) awscdk.Stack {
	var sprops awscdk.StackProps
	if props != nil {
		sprops = props.StackProps
	}
	stack := awscdk.NewStack(scope, &id, &sprops)

	helloHandler := awslambda.NewFunction(stack, jsii.String("HelloHandler"), &awslambda.FunctionProps{
		Code:    awslambda.Code_FromAsset(jsii.String("lambda"), nil),
		Runtime: awslambda.Runtime_NODEJS_16_X(),
		Handler: jsii.String("hello.handler"),
	})

	hitcounter := hitcounter.NewHitCounter(stack, "HelloHitCounter", &hitcounter.HitCounterProps{
		Downstream: helloHandler,
	})

	awsapigateway.NewLambdaRestApi(stack, jsii.String("Endpoint"), &awsapigateway.LambdaRestApiProps{
		Handler: hitcounter.Handler(),
	})

	return stack
}

func main() {
	defer jsii.Close()

	app := awscdk.NewApp(nil)

	NewCdkWorkshopStack(app, "CdkWorkshopStack", &CdkWorkshopStackProps{})

	app.Synth(nil)
}
{{</highlight>}}

Notice that we changed our API Gateway handler to `hitcounter.Handler()`
instead of `helloHandler`. This basically means that whenever our endpoint is hit, API
Gateway will route the request to our hit counter handler, which will log the
hit and relay it over to the `helloHandler` function. Then, the responses will be
relayed back in the reverse order all the way to the user.

## Deploy

```
cdk deploy
```
It might take a little while.

And the output:

```
CdkWorkshopStack.Endpoint8024A810 = https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/
```

## Test

Okay, ready to give this a go? (you should, again, see the URL of your API in
the output of the "deploy" command).

Use `curl` or your web browser to hit your endpoint (we use `-i` to show HTTP
response fields and status code):

```
curl -i https://xxxxxxxxxx.execute-api.us-east-1.amazonaws.com/prod/
```

Oh no... seems like something went wrong:

```
HTTP/2 502 Bad Gateway
...

{"message": "Internal server error"}
```

Let's see how to find out what happened and fix it.