sam local start-api , windows, golang lambda, not starting delve inside the container

[dan-dragan]

Hi everyone,
need help with debugging locally (attaching, breakpoints) a golang lambda on windows using VSCode.
The lambda handles a API Gateway post:

func handler(ctx context.Context, request events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
// Parse form data from the request body
parsedFormData, err := url.ParseQuery(request.Body)
if err != nil {
log.Printf("Error parsing form data: %s", err)
return events.APIGatewayProxyResponse{StatusCode: 400}, err
}
// Access POST parameters
key1 := parsedFormData.Get("key1")
key2 := parsedFormData.Get("key2")

log.Printf("Received Key1: %s", key1)
log.Printf("Received Key2: %s", key2)

return events.APIGatewayProxyResponse{
StatusCode: 200,
Body: fmt.Sprintf(%s %s, key1, key2),
}, nil
}

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

the template used is as follows:

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: Description of your lambda function
Globals:
Function:
Timeout: 5
Resources:
LambdaPostFunction:
Type: AWS::Serverless::Function
Properties:
Handler: bootstrap
Runtime: go1.x
CodeUri: ./
Events:
LambdaEndpoint:
Type: Api
Properties:
Path: /my-function-path
Method: post

commands used ( in bash):

export ARTIFACTS_DIR= $(shell pwd)/.aws-sam/build/LambdaPostFunction/
GOOS=linux GOARCH=amd64 go build -v -gcflags='all=-N -l' -o bootstrap
cp ./bootstrap $(ARTIFACTS_DIR)/bootstrap
mkdir -p dlv
go get github.com/go-delve/delve/cmd/dlv
GOOS=linux GOARCH=amd64 go build -v -gcflags='all=-N -l' -o dlv/dlv github.com/go-delve/delve/cmd/dlv
sam.cmd local start-api -d 9989 --debugger-path ./dlv --debug-args=-delveAPI=2 --warm-containers EAGER

output (I can POST to the dev server URL at 127.0.0.1:3000/ using POSTMAN) :

No current session found, using default AWS::AccountId
Initializing the lambda functions containers.
Falling back to a previous version of the emulation image
Local image is up-to-date
Using local image: public.ecr.aws/lambda/go:1-rapid-x86_64.

Mounting C:\Work\repos\Golang\go-lambda.aws-sam\build\LambdaPostFunction as /var/task:ro,delegated, inside
runtime container
Containers Initialization is done.
Mounting LambdaPostFunction at http://127.0.0.1:3000/my-function-path [POST]
You can now browse to the above endpoints to invoke your functions. You do not need to restart/reload SAM
CLI while working on your functions, changes will be reflected instantly/automatically. If you used sam
build before running local commands, you will need to re-run sam build for the changes to be picked up. You
only need to restart SAM CLI if you update your AWS SAM template
2025-04-17 14:10:55 WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.

• Running on http://127.0.0.1:3000
  2025-04-17 14:10:55 Press CTRL+C to quit
  Invoking bootstrap (go1.x)
  Reuse the created warm container for Lambda function 'LambdaPostFunction'
  Lambda function 'LambdaPostFunction' is already running
  START RequestId: 673c6dd0-f20c-48f7-92ae-392afb8337f5 Version: $LATEST
  2025/04/17 19:11:13 Received Key1: value1
  2025/04/17 19:11:13 Received Key2: value2
  END RequestId: 9b59c417-46a2-4e9c-b456-49fe2db84050
  REPORT RequestId: 9b59c417-46a2-4e9c-b456-49fe2db84050 Init Duration: 0.64 ms Duration: 1009.57 ms Billed Duration: 1010 ms Memory Size: 128 MB Max Memory Used: 128 MB

My launch.json:

{
// Use IntelliSense to learn about possible attributes.
// Hover to view descriptions of existing attributes.
// For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
"version": "0.2.0",
"configurations": [
{
"name": "Connect to server",
"type": "go",
"request": "attach",
"mode": "remote",
//"remotePath": "${workspaceFolder}",
"remotePath": "/var/task",
"port": 9989,
"host": "127.0.0.1",
"dlvFlags": ["--listen=127.0.0.1:9989", "--accept-multiclient", "--headless", "--api-version=2","--log"],
"trace": "verbose"
}
]
}

when choosing vscode\Run\ StartDebugging I get the following output:

AttachRequest
Start remote debugging: connecting 127.0.0.1:9989
To client: {"seq":0,"type":"event","event":"initialized"}
InitializeEvent
To client: {"seq":0,"type":"response","request_seq":2,"command":"attach","success":true}
Socket connection to remote was closed
Sending TerminatedEvent as delve is closed
To client: {"seq":0,"type":"event","event":"terminated"}
From client: configurationDone(undefined)
ConfigurationDoneRequest
From client: disconnect({"restart":false})

a 'ps aux' inside the local lambda container shows indeed no delve running, but the 'bootstrap' lambda binary is running:

sh-4.2# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.0 1231520 9972 ? Ssl 19:10 0:00 /var/rapid/aws-lambda-rie --log-level error
root 14 0.0 0.0 115512 3316 pts/0 Ss 19:11 0:00 /bin/sh
root 23 0.3 0.0 1421156 12516 ? Sl 19:11 0:00 /var/task/bootstrap
root 31 0.0 0.0 117368 2468 pts/0 R+ 19:11 0:00 ps aux

As I understand it, starting the lambda in debug mode with the (linux) dlv binary available should result in the aws-sam local injecting the dlv in the container and running it and this is not happening. Note in the output of the sam local start api there is no pause to attach the debugger either or any output that delve is running on the assigned debug port (9989). I have been struggling with this for awhile, any idea is appreciated. Thanks in advance.