How to create AWS Lambda Function with Go

Published: at 06:06 PM

Introduction

In this tutorial, we will walk you through the steps to create an AWS Lambda function that runs a Go binary using a custom runtime.

Table of contents

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Write Your Go Code

First, create a Go application. Below is an example of a Go function that handles a simple request:

package main

import (
    "context"
    "fmt"
    "github.com/aws/aws-lambda-go/lambda"
)

type MyEvent struct {
    Name string `json:"name"`
}

func HandleRequest(ctx context.Context, event MyEvent) (string, error) {
    return fmt.Sprintf("Hello, %s!", event.Name), nil
}

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

Build the Go Binary

Build a statically linked binary for Linux to make sure it’s compatible with AWS Lambda:

CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -o main main.go

Create a Custom Runtime for Lambda

Create an executable script named bootstrap to serve as the entry point for your Lambda function:

#!/bin/sh

set -e

# Execute the Go binary
./main

Make the bootstrap file executable:

chmod +x bootstrap

Create Deployment Package

Create a deployment package (ZIP file) that includes your Go binary and the bootstrap file:

zip function.zip main bootstrap

Create an IAM Role

You need an IAM role with the necessary permissions for your Lambda function. Follow these steps to create one:

Using the AWS Management Console

Open the IAM Console: Navigate to the IAM console at https://console.aws.amazon.com/iam/.

Create a New Role:

Select Trusted Entity:

Attach Permissions Policies:

Add Tags (Optional):

Name and Review Your Role:

Using the AWS CLI

Alternatively, you can create the IAM role using the AWS CLI:

Create a trust policy file named trust-policy.json:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

Create the role and attach the policy to that role:

aws iam create-role --role-name LambdaBasicExecutionRole --assume-role-policy-document file://trust-policy.json
aws iam attach-role-policy --role-name LambdaBasicExecutionRole --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole

Create the Lambda Function

Create the Lambda function using the provided.al2 runtime:

aws lambda create-function --function-name MyGoLambdaFunction \
--zip-file fileb://function.zip --handler bootstrap \
--runtime provided.al2 --role arn:aws:iam::YOUR_ACCOUNT_ID:role/LambdaBasicExecutionRole

Replace YOUR_ACCOUNT_ID with your AWS account ID.

Invoke the Lambda Function

Test the function using the AWS CLI:

aws lambda invoke --function-name MyGoLambdaFunction --payload eyJuYW1lIjogIldvcmxkIn0K response.json
cat response.json

Note: Payload is Base64 encoded.

Summary

In this tutorial, we covered the steps to create an AWS Lambda function that runs a Go binary using a custom runtime. First, we wrote a simple Go application and then built a statically linked binary for Linux. Next, we created a custom runtime using a bootstrap shell script to run our binary. We then packaged the binary and bootstrap script into a ZIP file for deployment.

To ensure our Lambda function had the necessary permissions, we created an IAM role. We showed how to do this in the AWS Management Console and the AWS CLI. After establishing the role, we created the Lambda function using the provided.al2 runtime and deployed our package. Finally, we tested the Lambda function by invoking it with a sample payload using the AWS CLI.

References