build: make Go 1.18 the min version, update to Go 1.19

As usual, we keep with the last two Go versions, which means the last
year of Go release (they release every 6 months or so).

This change means we can now use the type params (generics) in the
project!

dev.Dockerfile

@@ -4,7 +4,7 @@
 # /make/builder.Dockerfile
 # /.github/workflows/main.yml
 # /.github/workflows/release.yml
-FROM golang:1.18.2-alpine as builder
+FROM golang:1.19-alpine as builder
 
 LABEL maintainer="Olaoluwa Osuntokun <laolu@lightning.engineering>"