Switch to structured logging using slog

[TrevorSquillario]

https://go.dev/blog/slog

The new log/slog package in Go 1.21 brings structured logging to the standard library. This will help when deployed to Kubernetes and aggregating logs. I may work up a PR for this one.

import "log/slog"

func main() {
    slog.Info("hello, world")
}