package main

import (
        "fmt"
        "math/rand"
        "net/http"
        "regexp"
)

func handler(w http.ResponseWriter, r *http.Request) {
        ua := r.UserAgent()
        matched, err := regexp.Match("curl", []byte(ua))
        // not curl.
        if (err != nil) || !matched {
                fmt.Fprintf(w, "Curl to shell, if you dare.")
                return
        }
        // curl.
        if rand.Intn(6) == 5 {
                fmt.Fprintf(w, "echo \"bang\"")
        } else {
                fmt.Fprintf(w, "echo \"click\"")
        }
}

func main() {
        http.HandleFunc("/", handler)
        http.ListenAndServe(":8080", nil)
}