In this example we’ll look at how to create a serverless REST API with Golang on AWS using Serverless Stack (SST).

Requirements

Create an SST app

Let’s start by creating an SST app.

$ npm init sst -- go-starter rest-api-go
$ cd rest-api-go

By default our app will be deployed to an environment (or stage) called dev and the us-east-1 AWS region. This can be changed in the sst.json in your project root.

{
  "name": "rest-api-go",
  "region": "us-east-1",
  "main": "stacks/index.ts"
}

Project layout

An SST app is made up of two parts.

  1. stacks/ — App Infrastructure

    The code that describes the infrastructure of your serverless app is placed in the stacks/ directory of your project. SST uses AWS CDK, to create the infrastructure. CDK doesn’t currently support Golang, so we’ll be using JavaScript here.

  2. backend/ — App Code

    The code that’s run when your API is invoked is placed in the backend/ directory of your project. We’ll be using Golang for this.

Setting up our routes

Let’s start by setting up the routes for our API.

Replace the stacks/MyStack.ts with the following.

import { Api, StackContext } from "@serverless-stack/resources";

export function MyStack({ stack }: StackContext) {
  // Create the HTTP API
  const api = new Api(stack, "Api", {
    routes: {
      "GET /notes": "functions/list.go",
      "GET /notes/{id}": "functions/get.go",
      "PUT /notes/{id}": "functions/update.go",
    },
  });

  // Show API endpoint in output
  stack.addOutputs({
    ApiEndpoint: api.url,
  });
}

We are creating an API here using the Api construct. And we are adding three routes to it.

GET /notes
GET /notes/{id}
PUT /notes/{id}

The first is getting a list of notes. The second is getting a specific note given an id. And the third is updating a note.

Adding function code

For this example, we are not using a database. We’ll look at that in detail in another example. So internally we are just going to get the list of notes from a file.

Let’s add a file that contains our notes in backend/db/notes.go.

package db

import (
	"strconv"
	"time"
)

func Notes() map[string]map[string]string {
	return map[string]map[string]string{
		"id1": {
			"noteId":    "id1",
			"userId":    "user1",
			"content":   "Hello World!",
			"createdAt": strconv.FormatInt(time.Now().Unix(), 10),
		},
		"id2": {
			"noteId":    "id2",
			"userId":    "user2",
			"content":   "Hello Old World!",
			"createdAt": strconv.FormatInt(time.Now().Unix()-1000, 10),
		},
	}
}

Now add the code for our first endpoint.

Getting a list of notes

Add a backend/functions/list.go.

package main

import (
	"encoding/json"
	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
	"github.com/serverless-stack/examples/rest-api-go/db"
)

func Handler(request events.APIGatewayV2HTTPRequest) (events.APIGatewayProxyResponse, error) {
	response, _ := json.Marshal(db.Notes())

	return events.APIGatewayProxyResponse{
		Body:       string(response),
		StatusCode: 200,
	}, nil
}

func main() {
	lambda.Start(Handler)
}

Here we are simply converting a list of notes to string, and responding with that in the request body.

Getting a specific note

Add the following to backend/functions/get.go.

package main

import (
	"encoding/json"
	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
	"github.com/serverless-stack/examples/rest-api-go/db"
)

func Handler(request events.APIGatewayV2HTTPRequest) (events.APIGatewayProxyResponse, error) {
	var notes = db.Notes()
	var note = notes[request.PathParameters["id"]]

	if note == nil {
		return events.APIGatewayProxyResponse{
			Body:       `{"error":true}`,
			StatusCode: 404,
		}, nil
	}

	response, _ := json.Marshal(note)

	return events.APIGatewayProxyResponse{
		Body:       string(response),
		StatusCode: 200,
	}, nil
}

func main() {
	lambda.Start(Handler)
}

Here we are checking if we have the requested note. If we do, we respond with it. If we don’t, then we respond with a 404 error.

Updating a note

Add the following to backend/functions/update.go.

package main

import (
	"encoding/json"
	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
	"github.com/serverless-stack/examples/rest-api-go/db"
)

func Handler(request events.APIGatewayV2HTTPRequest) (events.APIGatewayProxyResponse, error) {
	var notes = db.Notes()
	var note = notes[request.PathParameters["id"]]

	if note == nil {
		return events.APIGatewayProxyResponse{
			Body:       `{"error":true}`,
			StatusCode: 404,
		}, nil
	}

	var body map[string]string
	_ = json.Unmarshal([]byte(request.Body), &body)

	note["content"] = body["content"]

	response, _ := json.Marshal(note)

	return events.APIGatewayProxyResponse{
		Body:       string(response),
		StatusCode: 200,
	}, nil
}

func main() {
	lambda.Start(Handler)
}

We first check if the note with the requested id exists. And then we update the content of the note and return it. Of course, we aren’t really saving our changes because we don’t have a database!

Now let’s test our new API.

Starting your dev environment

SST features a Live Lambda Development environment that allows you to work on your serverless apps live.

$ npm start

The first time you run this command it’ll take a couple of minutes to deploy your app and a debug stack to power the Live Lambda Development environment.

===============
 Deploying app
===============

Preparing your SST app
Transpiling source
Linting source
Deploying stacks
manitej-rest-api-go-my-stack: deploying...

 ✅  manitej-rest-api-go-my-stack


Stack manitej-rest-api-go-my-stack
  Status: deployed
  Outputs:
    ApiEndpoint: https://rxk5buowgi.execute-api.us-east-1.amazonaws.com

The ApiEndpoint is the API we just created.

Let’s test our endpoint using the integrated SST Console. The SST Console is a web based dashboard to manage your SST apps Learn more about it in our docs.

Go to the API explorer and click the Send button of the GET /notes route to get a list of notes.

Note, The API explorer lets you make HTTP requests to any of the routes in your Api construct. Set the headers, query params, request body, and view the function logs with the response.

API tab get notes response

You should see the list of notes as a JSON string.

To retrieve a specific note, Go to GET /notes/{id} route and in the URL tab enter the id of the note you want to get in the id field and click the Send button to get that note.

API tab get specific note response

Now to update our note, we need to make a PUT request, go to PUT /notes/{id} route.

In the URL tab, enter the id of the note you want to update and in the body tab and enter the below json value and hit Send.

{ "content": "Updating my note" }

API tab update note response

This should respond with the updated note.

Making changes

Let’s make a quick change to our API. It would be good if the JSON strings are pretty printed to make them more readable.

Replace Handler function in backend/functions/list.go with the following.

func Handler(request events.APIGatewayV2HTTPRequest) (events.APIGatewayProxyResponse, error) {
	response, _ := json.MarshalIndent(db.Notes(), "", "  ")

	return events.APIGatewayProxyResponse{
		Body:       string(response),
		StatusCode: 200,
	}, nil
}

Here we are just adding some spaces to pretty print the JSON.

If you head back to the GET /notes route and hit Send again.

API tab get notes response with spaces You should see your list of notes in a more readable format.

Deploying your API

To wrap things up we’ll deploy our app to prod.

$ npm run deploy -- --stage prod

This allows us to separate our environments, so when we are working in dev, it doesn’t break the app for our users.

Once deployed, you should see something like this.

 ✅  prod-rest-api-go-my-stack


Stack prod-rest-api-go-my-stack
  Status: deployed
  Outputs:
    ApiEndpoint: https://ck198mfop1.execute-api.us-east-1.amazonaws.com

Run the below command to open the SST Console in prod stage to test the production endpoint.

npm run console -- --stage prod

Go to the API explorer and click Send button of the GET /notes route, to send a GET request.

Prod API explorer get notes response with spaces

Cleaning up

Finally, you can remove the resources created in this example using the following commands.

$ npm run remove
$ npm run remove -- --stage prod

Conclusion

And that’s it! You’ve got a brand new serverless API. A local development environment, to test and make changes. And it’s deployed to production as well, so you can share it with your users. Check out the repo below for the code we used in this example. And leave a comment if you have any questions!