<form action="/upload" method="post" enctype="multipart/form-data">
  <input type="file" name="file" />
  <button type="submit">上传文件</button>
</form>

package main

import (
    "io"
    "net/http"
    "os"
)

func uploadHandler(w http.ResponseWriter, r *http.Request) {
    if r.Method != "POST" {
        http.Error(w, "只允许POST请求", http.StatusMethodNotAllowed)
        return
    }

    file, header, err := r.FormFile("file")
    if err != nil {
        http.Error(w, "无法获取文件", http.StatusBadRequest)
        return
    }
    defer file.Close()

    // 创建本地文件
    outFile, err := os.Create("./uploads/" + header.Filename)
    if err != nil {
        http.Error(w, "无法创建文件", http.StatusInternalServerError)
        return
    }
    defer outFile.Close()

    // 复制文件内容
    _, err = io.Copy(outFile, file)
    if err != nil {
        http.Error(w, "文件保存失败", http.StatusInternalServerError)
        return
    }

    w.WriteHeader(http.StatusOK)
    w.Write([]byte("文件上传成功"))
}

func main() {
    // 确保上传目录存在
    os.MkdirAll("./uploads", os.ModePerm)

    http.HandleFunc("/upload", uploadHandler)
    http.Handle("/", http.FileServer(http.Dir("."))) // 提供HTML页面
    http.ListenAndServe(":8080", nil)
}

func downloadHandler(w http.ResponseWriter, r *http.Request) {
    filename := r.URL.Query().Get("file")
    if filename == "" {
        http.Error(w, "缺少文件名参数", http.StatusBadRequest)
        return
    }

    filepath := "./uploads/" + filename

    // 检查文件是否存在
    if _, err := os.Stat(filepath); os.IsNotExist(err)">
        http.Error(w, "文件不存在", http.StatusNotFound)
        return
    }

    // 设置响应头，触发下载
    w.Header().Set("Content-Disposition", "attachment; filename="+filename)
    w.Header().Set("Content-Type", "application/octet-stream")

    // 输出文件
    http.ServeFile(w, r, filepath)
}

http.HandleFunc("/download", downloadHandler)