The state of AWS Lambda Go Streaming support

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
aws, go
Domain
backend, cloud

Research direction

Start by reproducing the documented lambda.Start example returning events.LambdaFunctionURLStreamingResponse with -tags lambda.norpc on the al2023 or provided runtime, using a Function URL configured with InvokeMode: RESPONSE_STREAM. Trace how the response is encoded and verify whether Body is serialized instead of streamed. Done means the documented Go response reaches the Function URL as streamed content, or the limitation and required runtime conditions are clearly documented.

Written by the indexing model from the issue text.

Description

question

Is your feature request related to a problem? Please describe.
I had been trying make the AWS Lambda response streaming work with aws-lambda-go runtime and I was not able to succeed. Neither the Lambda Function URLs or direct API call using InvokeWithResponseStream work and instead I was retrieving the entire response serialized to JSON.

I made my Lambda function return the events.LambdaFunctionURLStreamingResponse, but the entire response had been serialized and returned as JSON. The passed io.Reader had not been proceesed and suprisingly enough the response contain JSON serialized representation of the io.Reader implementation i.e.

{"StatusCode":200,"Headers":{"Content-Type":"application/octet-stream"},"Body":{"ReadCloser":{}},"Cookies":null}

I had been runing the GO Lambda function on al2023 runtime, compiled the binary with -tags lambda.norpc option and set up the Function URL.

FunctionUrl:
    Type: AWS::Lambda::Url
    Properties:
      TargetFunctionArn: !Ref Function
      AuthType: NONE
      InvokeMode: RESPONSE_STREAM

Neither of this had any impact and the behavior persisted. Even the documented in code example is not working correctly:

// Example:
//
//	lambda.Start(func() (*events.LambdaFunctionURLStreamingResponse, error) {
//		return &events.LambdaFunctionURLStreamingResponse{
//			StatusCode: 200,
//			Headers: map[string]string{
//				"Content-Type": "text/html",
//			},
//			Body: strings.NewReader("<html><body>Hello World!</body></html>"),
//		}, nil
//	})
//
// Note: This response type requires compiling with `-tags lambda.norpc`, or choosing the `provided` or `provided.al2` runtime.

Which results in response from Function URL:

{"StatusCode":200,"Headers":{"Content-Type":"text/html"},"Body":{},"Cookies":null}

Is Response Streaming not supported with Go runtime?

Describe the solution you'd like
I would like to use Lambda Response Streaming with my Go runtime.

Describe alternatives you've considered
I am not using AWS Lambda for this use case today.

Additional context
github.com/aws/aws-lambda-go v1.47.0

Dominant language
Go
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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