src-main.go

func main() {
  os.Chdir("/tmp") // Change working directory to /tmp so we can write files

  if len(os.Args) > 1 && os.Args[1] == "--test" {
    pdf2png()
  } else {
    lambda.Start(handler)
  }
}

func handler(ctx context.Context, s3Event events.S3Event) ([]string, error) {
  sess := session.Must(session.NewSession())

  bucket := s3Event.Records[0].S3.Bucket.Name
  key := s3Event.Records[0].S3.Object.Key

  if !strings.HasSuffix(strings.ToLower(key), ".pdf") {
    return nil, fmt.Errorf("Key does not look like a PDF file: %s", key)
  }
  convertKey := "converted/" + strings.TrimPrefix(key[:len(key)-4], "upload/") // trim ".pdf" off the end

  fmt.Println("Received S3 event, Bucket: ", bucket, ", Key: ", key, "Converting to: ", convertKey)

  // Will download the S3 object locally to /tmp/input.pdf
  if err := downloadPdf(sess, bucket, key); err != nil {
    return nil, err
  }

  // Convert to PNGs
  if err := pdf2png(); err != nil {
    return nil, err
  }

  // Upload all PNGs from /tmp/output to our converted/ key prefix
  return uploadPngs(sess, bucket, convertKey)
}