Building Serverless CRUD services in Go with DynamoDB - Part 4

Welcome back! It's been a while. Here's the part 4. In this post, we will create deleteHandler.go.

Getting started

First, let's add the config under functions in serverless.yml

delete:
    handler: bin/handlers/deleteHandler
    package:
      include:
        - ./bin/handlers/deleteHandler
    events:
      - http:
          path: iam/{id}
          method: delete
          cors: true

Create a file deleteHandler.go under src/handlers

Similarly, we have the below structure.

package main

import (
    "context"
    "fmt"
    "github.com/aws/aws-lambda-go/events"
    "github.com/aws/aws-lambda-go/lambda"
    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/dynamodb"
    "os"
)

var svc *dynamodb.DynamoDB

func init() {
    region := os.Getenv("AWS_REGION")
    // Initialize a session
    if session, err := session.NewSession(&aws.Config{
        Region: ®ion,
    }); err != nil {
        fmt.Println(fmt.Sprintf("Failed to initialize a session to AWS: %s", err.Error()))
    } else {
        // Create DynamoDB client
        svc = dynamodb.New(session)
    }
}

func Delete(ctx context.Context, request events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
    var (
        tableName = aws.String(os.Getenv("IAM_TABLE_NAME"))
        id        = aws.String(request.PathParameters["id"])
    )

    // TODO: Add delete logic
}

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

Deleting a record is pretty simple, we just need the record id (primary key) which can be retrieved from the request path parameters id.

func (c *DynamoDB) DeleteItem(input *DeleteItemInput) (*DeleteItemOutput, error)

In order to call DeleteItem API operation for Amazon DynamoDB, we need to build DeleteItemInput first.

input := &dynamodb.DeleteItemInput{
    Key: map[string]*dynamodb.AttributeValue{
        "id": {
            S: id,
        },
    },
    TableName: tableName,
}

If you define a composite primary key, you must provide values for both the partition key and the sort key. In this case, we just need to provide the first one. We also need to tell which table your records are located in.

call DeleteItem to delete a single item in a table by primary key

_, err := svc.DeleteItem(input)

if err != nil {
    fmt.Println("Got error calling DeleteItem:")
    fmt.Println(err.Error())

    // Status Internal Server Error
    return events.APIGatewayProxyResponse{
        Body:       err.Error(),
        StatusCode: 500,
    }, nil
}

// Status No Content
return events.APIGatewayProxyResponse{
    StatusCode: 204,
}, nil

Run the below command to deploy our code

./scripts/deploy.sh

Testing

If you go to AWS Lambda Console, you will see there is a function called serverless-iam-dynamodb-dev-delete

You can test your code either in Lambda or API Gateway.

Upon the success deletion, you should see that the status code returns 204.

That's it for part 4. In the next post, we'll create authHandler.go to secure our APIs.