Second Attempt: Responding with protobuf

main.go

func handler(request events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
	message := &api.AliveResponse{Message: "Hello, world."}

	b, err := proto.Marshal(message)
	if err != nil {
		return events.APIGatewayProxyResponse{
			StatusCode: 500,
		}, err
	}

	return events.APIGatewayProxyResponse{
		Body: base64.StdEncoding.EncodeToString(b),
		Headers: map[string]string{
			"Content-Type": "application/grpc+proto",
			"grpc-status":  "0",
		},
		IsBase64Encoded: true,
		StatusCode:      200,
	}, nil
}