cal/main.go

package main

import (
	"embed"
	"fmt"
	"html/template"
	"io"
	"io/fs"
	"mime"
	"net/http"
	"path/filepath"
)

//go:embed static
var staticFiles embed.FS

func main() {
    staticFS := fs.FS(staticFiles)
    http.HandleFunc("GET /", index)
    http.Handle("GET /static/{file}", http.FileServer(http.FS(staticFS)))

    if err := http.ListenAndServe(":4321", nil); err != nil {
        fmt.Printf("Unable to serve: %v\n", err)
    }
}

func serveFile(system fs.FS) func(w http.ResponseWriter, r http.Request) {
    return func(w http.ResponseWriter, r http.Request) {
        file := r.PathValue("file")
        reader, err := system.Open(file)

        if err != nil {
            http.Error(w, "File not found", 404)
            return
        }
        defer reader.Close()

        cont, err := io.ReadAll(reader)
        handleHTTPError("Error reading file", err, w)
        contType := mime.TypeByExtension(filepath.Ext(file))
        w.Header().Add("Content-Type", contType)
        _, err = w.Write(cont)
        handleHTTPError("Error writing HTTP resp", err, w)
    }
}

func index(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "text/html; charset=utf8")
    tmpl, err := template.ParseFiles("./tmpl/index.html", "./tmpl/base.html")
    handleHTTPError("Error parsing template", err, w)

    err = tmpl.Execute(w, nil)
    handleHTTPError("Error executing on template", err, w)
}

func handleHTTPError(msg string, err error, w http.ResponseWriter) {
    if err != nil {
        fmt.Printf("%v: %v", msg, err)
        http.Error(w, "Internal server error", 500)
        return
    }
}