AWS Node version is unsupported

[barklund]

The nodejs version specified (nodejs8.10) for AWS is now unsupported (as per Jan 6, 2020). Attempting to deploy to AWS gives this error:

The runtime parameter of nodejs8.10 is no longer supported
for creating or updating AWS Lambda functions. We recommend
you use the new runtime (nodejs12.x) while creating or updating
functions.

Updating to nodejs12.x as suggested in sam-template.json seems to work.