Golang如何通过POST请求上传包含文件的multipart/form-data？

package main

import (
    "bytes"
    "fmt"
    "io"
    "mime/multipart"
    "net/http"
    "os"
)

func main() {
    url := "http://example.com/upload" // 替换为您的上传地址
    filePath := "file.txt"             // 替换为您的文件路径

    file, err := os.Open(filePath)
    if err != nil {
        fmt.Println("Error opening file:", err)
        return
    }
    defer file.Close()

    body := &bytes.Buffer{}
    writer := multipart.NewWriter(body)
    part, err := writer.CreateFormFile("file", filePath)
    if err != nil {
        fmt.Println("Error creating form file:", err)
        return
    }
    _, err = io.Copy(part, file)
    if err != nil {
        fmt.Println("Error copying file content:", err)
        return
    }

    err = writer.Close()
    if err != nil {
        fmt.Println("Error closing writer:", err)
        return
    }

    req, err := http.NewRequest("POST", url, body)
    if err != nil {
        fmt.Println("Error creating request:", err)
        return
    }
    req.Header.Set("Content-Type", writer.FormDataContentType())

    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
        fmt.Println("Error sending request:", err)
        return
    }
    defer resp.Body.Close()

    respBody, err := io.ReadAll(resp.Body)
    if err != nil {
        fmt.Println("Error reading response body:", err)
        return
    }

    fmt.Println("Response:", string(respBody))
}