package main

import (
    "crypto/tls"
    "fmt"
    "log"
    "net/http"
    "time"
)

func Server(w http.ResponseWriter, req *http.Request) {
    // If a response is written, the issue isn't triggered.
    // io.WriteString(w, "hello, world!\n")
}

func Client(url string) {
    req, err := http.NewRequest("GET", url, nil)
    if err != nil {
        log.Fatal(err)
    }

    // This transport is what's causing unclosed connections.
    tr := &http.Transport{
        TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
    }
    hc := &http.Client{Timeout: 2 * time.Second, Transport: tr}

    resp, err := hc.Do(req)
    if err != nil {
        log.Fatal(err)
    }
    defer resp.Body.Close()
}

func main() {
    // Wait a bit and launch one client every second.
    // On the terminal, run `ss | grep :8000` to see
    // ESTABLISHED connections grow with every request.

    go func() {
        time.Sleep(1 * time.Second)

        n := 0
        for {
            Client("http://localhost:8000")
            fmt.Println("Request", n)
            n += 1

            time.Sleep(1 * time.Second)
        }
    }()

    http.HandleFunc("/", Server)
    log.Fatal(http.ListenAndServe(":8000", nil))
}