Golang を使用して HTTP ファイルのダウンロードを処理するにはどうすればよいですか?

import (
    "log"
    "net/http"
)

func main() {
    fs := http.FileServer(http.Dir("./files"))
    http.Handle("/files/", http.StripPrefix("/files", fs))
    log.Fatal(http.ListenAndServe(":8080", nil))
}

import (
    "log"
    "net/http"

    "github.com/CloudyKit/jet/v6"
)

func main() {
    engine := jet.NewEngine()
    http.Handle("/", engine)
    log.Fatal(http.ListenAndServe(":8080", nil))
}

import (
    "log"
    "net/http"
    "os"

    "github.com/CloudyKit/jet/v6"
)

func main() {
    engine := jet.NewEngine()
    engine.Get("/", func(c *jet.Context) error {
        filePath, err := filepath.Abs("file.txt")
        if err != nil {
            return err
        }
        f, err := os.Open(filePath)
        if err != nil {
            return err
        }
        defer f.Close()
        return engine.ServeContent(c.ResponseWriter(), c.Request(), "file.txt", time.Now(), f)
    })
    log.Fatal(http.ListenAndServe(":8080", engine))
}

package main

import (
    "log"
    "net/http"

    "github.com/CloudyKit/jet/v6"
)

type fileStore struct {
    files map[string][]byte
}

func main() {
    fs := &fileStore{files: make(map[string][]byte)}
    engine := jet.NewEngine()
    engine.Get("/", func(c *jet.Context) error {
        // 返回可用文件列表
    })
    engine.Post("/", func(c *jet.Context) error {
        // 将文件保存到文件存储中
    })
    engine.Get("/download/:file", func(c *jet.Context) error {
        file := c.Params["file"]
        data, ok := fs.files[file]
        if !ok {
            return http.StatusNotFound
        }
        return engine.ServeContent(c.ResponseWriter(), c.Request(), file, time.Now(), data)
    })
    log.Fatal(http.ListenAndServe(":8080", engine))
}