Extract Go version from go.mod

go-mod-version.sh

# These have been tested against:
#  macOS 12.6 / built-in
#  Alpine 3.16.2 / BusyBox v1.35
#  Debian 11.5 / GNU sed v4.7

# short, readable, should be fine for most purposes!
sed -n -e 's/^go \(.*\)$/\1/p' go.mod

# strict based on https://go.dev/ref/mod#go-mod-file-go
# > The version must be a valid Go release version: a positive
# > integer followed by a dot and a non-negative integer
# > (for example, 1.9, 1.14).
sed -n -e 's/^go \([[:digit:]][[:digit:]]*\.[[:digit:]][[:digit:]]*\)$/\1/p' go.mod

vars.mk

# don't forget to escape the $ in Makefile!
GO_VERSION=$(shell sed -n -e 's/^go \(.*\)$$/\1/p' go.mod)