How to Fix \'Bad Request: there is no photo in the request\' Error When Uploading Files with Go\'s POST Requests?

Uploading Files with POST Requests in Go

In Go, you can use an HTTP POST request to upload files to a remote server. When using Telegram's bot API, you may encounter an error message stating "Bad Request: there is no photo in the request." This indicates that the file data is not being included in the request correctly.

To fix this issue, you need to format the POST request as a multipart/form-data request. This allows you to include both text parameters and binary file data in the same request. Here's an updated version of your code that includes the required modifications:

<code class="go">import (
    "bytes"
    "io"
    "mime/multipart"
    "net/http"
    "path/filepath"
)

// content is a struct which contains a file's name, its type and its data.
type content struct {
    fname string
    ftype string
    fdata []byte
}

func sendPostRequest(url string, files ...content) ([]byte, error) {
    var (
        buf = new(bytes.Buffer)
        w   = multipart.NewWriter(buf)
    )

    for _, f := range files {
        part, err := w.CreateFormFile(f.ftype, filepath.Base(f.fname))
        if err != nil {
            return []byte{}, err
        }

        _, err = part.Write(f.fdata)
        if err != nil {
            return []byte{}, err
        }
    }

    err := w.Close()
    if err != nil {
        return []byte{}, err
    }

    req, err := http.NewRequest("POST", url, buf)
    if err != nil {
        return []byte{}, err
    }
    req.Header.Add("Content-Type", w.FormDataContentType())

    client := &http.Client{}
    res, err := client.Do(req)
    if err != nil {
        return []byte{}, err
    }
    defer res.Body.Close()

    cnt, err := io.ReadAll(res.Body)
    if err != nil {
        return []byte{}, err
    }
    return cnt, nil
}</code>

This updated code:

• Creates a multipart.Writer to construct the multipart/form-data request.
• Adds each file to the request using CreateFormFile.
• Closes the multipart writer to complete the request construction.
• Sets the content type header to multipart/form-data.
• Sends the request and retrieves the response from Telegram.

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