Tiny standalone daemon to accept HTTP requests on port 80 and redirect client to HTTPS

redirector.go

package main

import (
	"fmt"
	"net/http"
	"os"
	"strings"
)

func redirect(w http.ResponseWriter, req *http.Request) {
	parts := strings.SplitN(req.Host, ":", 2)
	host := parts[0]
	if host == "" {
		w.WriteHeader(400)
		w.Write([]byte("Invalid request, Host header missing"))
		return
	}
	location := "https://" + host + req.URL.Path
	w.Header().Set("Location", location)
	w.WriteHeader(301)
}

func main() {
	http.HandleFunc("/", redirect)
	err := http.ListenAndServe(":80", nil)
	fmt.Fprintln(os.Stderr, err)
	os.Exit(1)
}

redirector.service

[Unit]
Description=HTTP to HTTPS redirector
After=network-online.target multi-user.target
Wants=network-online.target

[Service]
ExecStart=/usr/local/sbin/redirector
User=nobody
AmbientCapabilities=CAP_NET_BIND_SERVICE
Restart=always
RestartSec=30

[Install]
WantedBy=multi-user.target