文件上传下载

1. 文件上传

使用 r.ParseMultipartForm 解析上传的文件：

func uploadHandler(w http.ResponseWriter, r *http.Request) {
    err := r.ParseMultipartForm(10 << 20) // 限制最大上传大小10MB
    if err != nil {
        http.Error(w, "File too big", http.StatusBadRequest)
        return
    }
    file, handler, err := r.FormFile("uploadFile")
    if err != nil {
        http.Error(w, "Error retrieving the file", http.StatusBadRequest)
        return
    }
    defer file.Close()
    dst, err := os.Create("./uploads/" + handler.Filename)
    if err != nil {
        http.Error(w, "Unable to save the file", http.StatusInternalServerError)
        return
    }
    defer dst.Close()
    io.Copy(dst, file)
    fmt.Fprintf(w, "File uploaded successfully: %s\n", handler.Filename)
}

`

2. 文件下载

设置响应头实现文件下载：

func downloadHandler(w http.ResponseWriter, r *http.Request) {
    filename := "example.txt"
    w.Header().Set("Content-Disposition", "attachment; filename="+filename)
    w.Header().Set("Content-Type", "application/octet-stream")
    http.ServeFile(w, r, "./files/"+filename)
}

文件上传和下载是 Web 应用中常见的功能，需注意安全和性能。