CODEWITHSUNDEEP
amazon-web-servicesgoaws-lambda
Doug Smith
Doug Smith

Reputation: 29316

Setting up AWS Lambda with Go, why do I always get "Internal server error" with this simple function?

I'm using literally the example function from the Go docs:

package main

import (
    "context"
    "fmt"

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

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

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

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

If I use the test event console and input { "name": "John" } it works fine.

But if I go to Add Triggers, click API Gateway, then click Create a new API, set Security to Open, leave everything else default, then click Add then Save.

If I see the URL it lists at the bottom as "API endpoint:" and click it, I get "Internal server error".

If I do curl -XPOST -d "{ \"name\": \"Paul\" }" https://AWS-URL-ENDPOINT/amazonaws.com/default/mytestfunction

I get "Internal server error".

What am I doing wrong?

Upvotes: 3

Views: 1150

Answers (2)

Josh Van de Walle
Josh Van de Walle

Reputation: 216

I had this issue and fixed it by using AWS structure types in my code.

I followed the sample function available here and using events.APIGatewayProxyRequest and events.APIGatewayProxyResponse from "github.com/aws/aws-lambda-go/events" as my DTOs. The APIGatewayProxyRequest is the parameter your handler needs and events.APIGatewayProxyResponse is what your handler needs to return.

Upvotes: 2

thomasmichaelwallace
thomasmichaelwallace

Reputation: 8464

One of the most common reasons to get Internal server error is that your Lambda function is either crashing or not returning what is expected by the triggering service.

In this case I suspect a bit of both.

When you proxy through API Gateway your event payload isn't just what you POST'ed. You can find out more about the shape of events here, including those of an API Gateway request: (https://docs.aws.amazon.com/lambda/latest/dg/eventsources.html#eventsources-api-gateway-request).

Your lambda is crashing because the event you get from API Gateway can not be cast into your type MyEvent struct, as it does not have a name property; in fact, the body of the request is actually in event.body as a string which has to be decoded.

A good guide to the events your expected for responses for API Gateway with lambda can be found here (https://serverless.com/framework/docs/providers/aws/events/apigateway/)

Upvotes: 5

Related Questions