All (but one) Lambda Runtimes now use the amzn-ami-hvm-2018.03.0.20181129-x86_64-gp2 AMI, as documented under the AWS Lambda Runtimes.
https://docs.aws.amazon.com/lambda/latest/dg/current-supported-versions.html
AWS has kindly provided us with it as a base docker image.
https://github.com/aws/amazon-linux-docker-images/tree/2018.03
You may note that Node.js 10 actually runs on AmazonLinux 2. We have not configured a build instance for that, but perhaps if there were enough demand we might in the future.