使用GoLang发送带有curl的分段请求

Question

I want to convert below code to golang.

curl -X POST
  'https://api.documo.com/v1/fax/send' \
  -H 'Authorization: Basic YOUR_API_KEY' \
  -H 'content-type: multipart/form-data' \
  -F 'recipientFax=12345678900' \
  -F 'coverPage=false' \
  -F 'recipientName=John' \
  -F 'subject=test' \
  -F 'notes=test' \
  -F '=@/home/user/Documents/Sample.pdf'

Please help

Below is my code what i have tried.

func SendFaxDocumo(files []*multipart.FileHeader, params map[string]string) {

    request, err := SendMultipartRequest("https://api.documo.com/v1/fax/send", params, files)
    if err != nil {
        fmt.Println(err.Error())

    }
    client := &http.Client{}
    resp, err := client.Do(request)
    if err != nil {
        fmt.Println(err.Error())
    } else {
        body := &bytes.Buffer{}
        _, err := body.ReadFrom(resp.Body)
        if err != nil {
            fmt.Println(err.Error())
        }
        resp.Body.Close()
        fmt.Println(resp.StatusCode)
        fmt.Println(resp.Header)
        fmt.Println(body)
    }
}

func SendMultipartRequest(uri string, params map[string]string, files []*multipart.FileHeader) (*http.Request, error) {

    body := &bytes.Buffer{}
    writer := multipart.NewWriter(body)

    for i, _ := range files {
        // string_index := strconv.Itoa(i)
        file, err := files[i].Open()
        defer file.Close()
        if err != nil {
            fmt.Println(err)
        }

        doc , err := ioutil.ReadAll(file)
        if err != nil {
            fmt.Println(err,980)
        }

        part, err := writer.CreateFormFile("file",files[i].Filename)

        if err != nil {
            fmt.Println(err)
        }

        part.Write([]byte(string(doc)))
        if _, err = io.Copy(part, file); err != nil {
            fmt.Println(err)
        }

        if err != nil {
            fmt.Println(err)
        }
    }

    for key, val := range params {
        _ = writer.WriteField(key, val)
    }

    err := writer.Close()
    if err != nil {
        return nil, err
    }

    req, err := http.NewRequest("POST", uri, body)
    req.Header.Set("Content-Type", writer.FormDataContentType())
    req.Header.Set("Authorization", "Basic my_key")

    return req, err
}

And the error i am getting is below: {"error":{"name":"Error","message":"File extension not allowed. Allowed formats: tiff,gif,png,jpeg,pdf,doc,xls,ppt,pcl,eps,ps,txt,rtf,xml,fxc,docx,pptx,xlsx"}}

This is the response got from the url requested even if i am trying it by pdf.