Lambda to read SNS event and send message to Slack using incoming webhook.

main.go

package main

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"

	"github.com/aws/aws-lambda-go/events"
	"github.com/aws/aws-lambda-go/lambda"
)

// NotifySlack sends message to Slack reading context
func NotifySlack(ctx context.Context, snsEvent events.SNSEvent) error {
	var data map[string]string
	var attachment string

	for _, record := range snsEvent.Records {
		snsRecord := record.SNS

		fmt.Printf("[%s %s] Message = %s \n", record.EventSource, snsRecord.Timestamp, snsRecord.Message)
		attachment = snsRecord.Message
	}
	json.Unmarshal([]byte(attachment), &data)

	webhookURL := "https://hooks.slack.com/services/XXXXXXXXXXX/YYYYYYYYYYY/ZZZZZZZZZZZZZZZZZZZZZZZ"

	requestBody, err := json.Marshal(map[string]interface{}{
		"text": "*" + data["NewStateValue"] + ":* " + data["AlarmName"],
		"blocks": []interface{}{
			map[string]interface{}{
				"type": "section",
				"text": map[string]string{
					"type": "mrkdwn",
					"text": "*RDS Free Storage Notification* \n" +
						"*" + data["NewStateValue"] + ":* " + data["AlarmName"],
				},
			},
			map[string]interface{}{
				"type": "section",
				"text": map[string]string{
					"type": "mrkdwn",
					"text": "> *AccountId:* " + data["AWSAccountId"] + "\n" +
						"> *AWS Region:* " + data["Region"] + "\n" +
						"> *Reason:* " + data["NewStateReason"],
				},
			},
		},
	})

	if err != nil {
		fmt.Printf("%s", err)
		return err
	}

	resp, err := http.Post(webhookURL, "application/json", bytes.NewBuffer(requestBody))
	if err != nil {
		fmt.Printf("%s", err)
		return err
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	fmt.Print(string(body))
	return nil
}

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