exec format error when running AWS Golang Lambda

Question

I have a go application, structured like this:

cmd
|
reports
|
main.go

main.go imports internal/reports package and has a single function, main(), which delegates call to aws-lambda-go/lambda.Start() function.

Code is build running the commands (snippet):

cd internal/reports && go build handler.go
cd ../..
go build -o reports ../cmd/reports/main.go && chmod +x reports && zip reports.zip reports

reports.zip is uploaded to AWS Lambda, which in turns throws an error when Test button is pressed:

{
  "errorMessage": "fork/exec /var/task/reports: exec format error",
  "errorType": "PathError"
}

reports is set as Lambda's Handler.

Also, code is build on Ubuntu 14.04 machine, as a part of aws/codebuild/ubuntu-base:14.04 Docker Image, on AWS CodeBuild. There should be no environment issues here, even though the error suggests a cross-platform problem.

Any ideas?

Caryophyllaceous

Answer 1

The issue is that main() function is not declared in main package, which is mandatory by Golang language spec

Caryophyllaceous

Thanks, this would have been really tough to catch given the error message. – Spillage

I completely missed your comment and wasted hours on this! Thank you for sharing. It was exactly this! – Corker

I have the same issue and i also declare main() function – Adept

Answer 2

You have to build with GOARCH=amd64 GOOS=linux. Wherever you build your binary, the binary for Lambda is run on Amazon Linux.

So , try this build command.

GOARCH=amd64 GOOS=linux go build handler.go

Taboo

hmm build in Windows 10 only works for me when "GOOS=", and then I have to set "GOARCH=amd64 GOOS=linux" to get build-lambda-zip.exe to work – Ibadan

running "go get -u golang.org/x/crypto/md4" fixed the issue for me, not sure why I had to do that – Ibadan

docs.aws.amazon.com/lambda/latest/dg/… gave the details I needed on Windows, but this answer pointed me there – Aetna

A lot of the Amazon documentation and online walkthroughs skip/ignore the GOARCH=amd64 piece. If you're on one of the new Mac M1 chips this is required. – Incisive