hdr_echo.go

package main

import (
    "fmt"
    "net/http"
)

func echoHeadersHandler(w http.ResponseWriter, r *http.Request) {
    // リクエストヘッダをレスポンスヘッダにコピー
    for name, values := range r.Header {
        for _, value := range values {
            w.Header().Add(name, value)
        }
    }
    fmt.Fprintln(w, "OK!")
}

func main() {
    http.HandleFunc("/", echoHeadersHandler)
    fmt.Println("Starting server on :8080...")
    if err := http.ListenAndServe(":8080", nil); err != nil {
        fmt.Printf("Server failed: %s\n", err)
    }
}

go build -o server hdr_echo.go 
sudo mv server /usr/local/bin/

/etc/systemd/system/server.service

[Unit]
Description=Simple Server Service
After=network.target

[Service]
ExecStart=/usr/local/bin/server
Restart=always
User=www-data
Group=www-data
Environment=PATH=/usr/local/bin:/usr/bin:/bin
WorkingDirectory=/usr/local/bin

[Install]
WantedBy=multi-user.target

sudo systemctl daemon-reload
sudo systemctl enable server.service
sudo systemctl start server.service
sudo systemctl status server.service