Build the container with Go 1.26

The runtime improvements in this version might be useful.

I realize GStreamer 1.28 is out, but I want to spend some time making
sure I understand the changes involved. They specifically had a note
about mpeg2dec being deprecated in favor of libavcodec. Which, now that
I think about it, is probably why the Alpine Linux maintainers stopped
shipping that plugin ages ago, which makes me a fool for building from
source instead of figuring out _why_ they stopped shipping it.

Author: featherbread

Dockerfile

@@ -1,8 +1,8 @@
-# syntax = docker.io/docker/dockerfile:1.20
+# syntax = docker.io/docker/dockerfile:1.21
 
 # The Alpine and Go base images must use the same release of Alpine.
 ARG ALPINE_BASE=docker.io/library/alpine:3.23
-ARG GOLANG_BASE=docker.io/library/golang:1.25-alpine3.23
+ARG GOLANG_BASE=docker.io/library/golang:1.26-alpine3.23
 # The Node.js image does not require any particular OS.
 ARG NODEJS_BASE=docker.io/library/node:24-alpine
 # See https://gstreamer.freedesktop.org/news/.