How to Fix the \'Bad Request: there is no photo in the request\' Error When Sending Files to Telegram Bots with Golang?

Sending a File with a POST Request in Golang for Telegram Bot Development

Problem: Error 'Bad Request: there is no photo in the request' while uploading a file

In an attempt to write a function for uploading a file to Telegram via a POST request, you encountered the error "Bad Request: there is no photo in the request." Your initial approach using the SendPostRequest function proved unsuccessful.

Improved Solution

After thorough research, the following improved solution was found:

<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)
    )

    // Iterate over the files and add them as form fields
    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
        }
    }

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

    // Create a new POST request
    req, err := http.NewRequest("POST", url, buf)
    if err != nil {
        return []byte{}, err
    }

    // Set the Content-Type header
    req.Header.Add("Content-Type", w.FormDataContentType())

    // Create a new HTTP client
    client := &http.Client{}

    // Send the request
    res, err := client.Do(req)
    if err != nil {
        return []byte{}, err
    }

    // Close the response body
    defer res.Body.Close()

    // Read the response body
    cnt, err := io.ReadAll(res.Body)
    if err != nil {
        return []byte{}, err
    }

    return cnt, nil
}</code>

This updated solution utilizes multipart form data to send the file, which resolves the issue and ensures that the file is present in the request.

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