package main

...

func (app *application) render(w http.ResponseWriter, r *http.Request, status int, page string, data templateData) {
    ts, ok := app.templateCache[page]
    if !ok {
        err := fmt.Errorf("the template %s does not exist", page)
        app.serverError(w, r, err)
        return
    }

    buf := new(bytes.Buffer)

    err := ts.ExecuteTemplate(buf, "base", data)
    if err != nil {
        app.serverError(w, r, err)
        return
    }
    
    // Deliberate error: set a Content-Length header with an invalid (non-integer) 
    // value.
    w.Header().Set("Content-Length", "this isn't an integer!")

    w.WriteHeader(status)

    buf.WriteTo(w)
}

...

package main

...

func main() {
    addr := flag.String("addr", ":4000", "HTTP network address")
    dsn := flag.String("dsn", "web:pass@/snippetbox?parseTime=true", "MySQL data source name")
    flag.Parse()

    logger := slog.New(slog.NewTextHandler(os.Stdout, nil))

    ...

    srv := &http.Server{
        Addr:     *addr,
        Handler:  app.routes(),
        // Create a *log.Logger from our structured logger handler, which writes
        // log entries at Error level, and assign it to the ErrorLog field. If 
        // you would prefer to log the server errors at Warn level instead, you
        // could pass slog.LevelWarn as the final parameter.
        ErrorLog: slog.NewLogLogger(logger.Handler(), slog.LevelError),
    }

    logger.Info("starting server", "addr", srv.Addr)

    err = srv.ListenAndServe()
    logger.Error(err.Error())
    os.Exit(1)
}

...

package main

...

func (app *application) render(w http.ResponseWriter, r *http.Request, status int, page string, data templateData) {
    ts, ok := app.templateCache[page]
    if !ok {
        err := fmt.Errorf("the template %s does not exist", page)
        app.serverError(w, r, err)
        return
    }

    buf := new(bytes.Buffer)

    err := ts.ExecuteTemplate(buf, "base", data)
    if err != nil {
        app.serverError(w, r, err)
        return
    }
    
    w.WriteHeader(status)

    buf.WriteTo(w)
}

...