How to fix Dockerfile FromAsCasing: 'as' and 'FROM' keywords' casing do not match

Problem

When building a Docker image, you see the following warning:

 1 warning found (use docker --debug to expand):
 - FromAsCasing: 'as' and 'FROM' keywords' casing do not match (line 2)

Solution

First note that this is just a warning, not an error. The build will work just fine if you ignore that.

The way to fix it is to find any line containing FROM and as like this one:

FROM hugomods/hugo as builder

and make sure that both FROM and as are uppercase:

FROM hugomods/hugo AS builder