html5原生js拖拽上传（golang版）

一次只能传一个文件，需在main.go同级目录中建一个upload文件夹
main.go
package main

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

const (
    upload_path string = "./upload/"
)

//上传
func uploadHandle(w http.ResponseWriter, r *http.Request) {
    if r.Method == "GET" {
        io.WriteString(w, tpl)
    } else {
        //获取文件内容 要这样获取
        file, head, err := r.FormFile("upfile")
        fmt.Println(file)
        if err != nil {
            fmt.Println(err)
            return
        }
        defer file.Close()
        //创建文件
        fW, err := os.Create(upload_path + head.Filename)
        if err != nil {
            fmt.Println("文件创建失败")
            return
        }
        defer fW.Close()
        _, err = io.Copy(fW, file)
        if err != nil {
            fmt.Println("文件保存失败")
            return
        }
        fmt.Println(w, head.Filename+" 保存成功")
        //io.WriteString(w, head.Filename+" 保存成功")
        //http.Redirect(w, r, "/success", http.StatusFound)
        //io.WriteString(w, head.Filename)
    }
}

func main() {
    fmt.Println("OK!请访问  :8080/upload")
    //启动一个http 服务器
    http.HandleFunc("/upload", uploadHandle)
    err := http.ListenAndServe(":8080", nil)
    if err != nil {
        fmt.Println("服务器启动失败")
        return
    }
}

var tpl = `<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>drag file</title>
</head>
<body>
    <div class="container"> 
        <div id="fileSpan" style="background-color:red;200px;height:200px"></div>
    </div>
    <script type="text/javascript">
window.onload = function(){  
     var uuz = document.getElementById('fileSpan');  

     uuz.ondragenter = function(e){  
         e.preventDefault();  
     }  

     uuz.ondragover = function(e){  
         e.preventDefault();  
         this.innerHTML = '请松开';  
    }  

     uuz.ondragleave = function(e){  
         e.preventDefault();  
         this.innerHTML = '请拖入要上传的文件';  
     }  

     uuz.ondrop = function(e){  
         e.preventDefault();  

         var upfile = e.dataTransfer.files[0]; //获取要上传的文件对象(可以上传多个) 
    alert(upfile.name)
alert(upfile.type)        
         var formdata = new FormData();  
         var xhr = new XMLHttpRequest();  
         formdata.append('upfile', upfile); //设置服务器端接收的name为upfile  
         xhr.open("post","upload");
         xhr.onreadystatechange = function(){ 
             if(this.readyState==4){
                 if(this.status==200){ //上传成功  
                     var resultText = this.responseText;
                     console.info(resultText);
                     //转json
                     var jsonObj = JSON.parse(resultText);
                     console.info(jsonObj);
                     if(jsonObj.success){
                         //生成input表单
                         var fileId = createInput(jsonObj.uuid);
                         //生成显示名称
                         appendFile1(fileId,upfile.name); 
                     }
                 }else{  
                     alert('上传失败,请使用另一种方式上传');  
                 }
             }
         }  

         xhr.send(formdata);  
     }  
 }
    </script>
</body>
</html>`
html部分参考：https://blog.csdn.net/nanfang1105/article/details/77965915
如需跨域，可参考：https://blog.csdn.net/benben_2015/article/details/79247024