go-server-useragent.go

package main

import (
    "fmt"
    "log"

    "flag"

    "net/http"

    "strconv"
)

var (
    port int
)

func rootHandler(w http.ResponseWriter, r *http.Request) {
    ua := r.Header.Get("User-Agent")

    msg := fmt.Sprintf("Your user agent is: %v\n", ua)

    w.Header().Set("Content-Type", "text/plain")
    w.Header().Set("Content-Length", strconv.Itoa(len(msg)))

    fmt.Fprint(w, msg)
}

func init() {
    flag.IntVar(&port, "port", 8080, "HTTP Server Port")

    flag.Parse()
}

func main() {
    httpAddr := fmt.Sprintf(":%v", port)

    log.Printf("Listening to %v", httpAddr)

    http.HandleFunc("/", rootHandler)
    log.Fatal(http.ListenAndServe(httpAddr, nil))
}

I think this one is missing a defer :P