golang模拟客户端上传文件到服务器

服务器端：

package main
import (
    "fmt"
    "log"
    "net/http"
    "strings"
    "time"
    "crypto/md5"
    "io"
    "strconv"
    "os"
)
func upload(w http.ResponseWriter, r *http.Request) {
    fmt.Println("method:", r.Method) //获取请求的方法
    if r.Method == "GET" {
        crutime := time.Now().Unix()
        h := md5.New()
        io.WriteString(h, strconv.FormatInt(crutime, 10))
        token := fmt.Sprintf("%x", h.Sum(nil))
        t, _ := template.ParseFiles("upload.gtpl")
        t.Execute(w, token)
    } else {
        r.ParseMultipartForm(32 << 20)
        file, handler, err := r.FormFile("uploadfile")
        if err != nil {
            fmt.Println(err)
            return
        }
        defer file.Close()
        fmt.Fprintf(w, "%v", handler.Header)
        f, err := os.OpenFile("./test/"+handler.Filename, os.O_WRONLY|os.O_CREATE, 0666)  // 此处假设当前目录下已存在test目录
        if err != nil {
            fmt.Println(err)
            return
        }
        defer f.Close()
        io.Copy(f, file)
    }
}
func main() {
    http.HandleFunc("/upload", upload)
    err := http.ListenAndServe(":8080", nil) //设置监听的端口
    if err != nil {
        log.Fatal("ListenAndServe: ", err)
    }
}

其实Go支持模拟客户端表单功能支持文件上传，详细用法请看如下示例：
客户端代码：

package main
import (
    "bytes"
    "fmt"
    "io"
    "io/ioutil"
    "mime/multipart"
    "net/http"
    "os"
)
func postFile(filename string, targetUrl string) error {
    bodyBuf := &bytes.Buffer{}
    bodyWriter := multipart.NewWriter(bodyBuf)
    //关键的一步操作
    fileWriter, err := bodyWriter.CreateFormFile("uploadfile", filename)
    if err != nil {
        fmt.Println("error writing to buffer")
        return err
    }
    //打开文件句柄操作
    fh, err := os.Open(filename)
    if err != nil {
        fmt.Println("error opening file")
        return err
    }
    defer fh.Close()
    //iocopy
    _, err = io.Copy(fileWriter, fh)
    if err != nil {
        return err
    }
    contentType := bodyWriter.FormDataContentType()
    bodyWriter.Close()
    resp, err := http.Post(targetUrl, contentType, bodyBuf)
    if err != nil {
        return err
    }
    defer resp.Body.Close()
    resp_body, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        return err
    }
    fmt.Println(resp.Status)
    fmt.Println(string(resp_body))
    return nil
}
// sample usage
func main() {
    target_url := "http://localhost:8080/upload"
    filename := "./test.png"
    postFile(filename, target_url)
}