Web proxy that disallows distracting websites

focus.go

package main

import (
        "flag"
        "fmt"
        "github.com/elazarl/goproxy"
        "log"
        "net/http"
        "os"
)

func main() {
        flag.Parse()
        if flag.NArg() != 1 {
                fmt.Println("usage: focus PORT")
                os.Exit(1)
        }
        portStr := flag.Arg(0)
        proxy := goproxy.NewProxyHttpServer()
        proxy.Verbose = true

        blacklist := []string {
                "www.reddit.com",
                "news.ycombinator.com",
                "www.youtube.com",
        }
        for _, host := range(blacklist) {
                proxy.OnRequest(goproxy.DstHostIs(host)).DoFunc(scold)
        }

        log.Fatal(http.ListenAndServe(":" + portStr, proxy))
}

func scold(r *http.Request,ctx *goproxy.ProxyCtx)(*http.Request,*http.Response) {
        return r, goproxy.NewResponse(r, goproxy.ContentTypeText,http.StatusForbidden,
                                      "Don't waste your time!")
}