sending struct to form field in golang

I have a struct which I have to send to an api and it's a post request. But the input are form field. And the fields contains strings, integer, float and image. I tried to use WriteField function but since this function only takes strings as parameters, I can't process integer and float. How do I do that. Here is my struct and the code snippet.

c := finalObject{
    name: Name,
    ProfilePic:"/img/unknown.jpg",
    owner:"Mr Hall",
    latitude:26.5473828,
    longitude:88.4249179,
    opendays:"Monday-Friday",
    openhours:"10am to 5pm",
    catId:82,
    address:address,
    phone_number:2312312,
    mobile_number:312312,
    email:"dsdas@a.com",
  }

  url := "https://abcd.com/a"
    fmt.Println("URL:>", url)
    b, err := json.Marshal(c)
    if err != nil {
      fmt.Println("error:", err)
    }
    os.Stdout.Write(b)
    var jsonStr = []byte(b)
    req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonStr))
    req.Header.Set("Authorization", "AUTH_TOKEN")
    req.Header.Set("enctype", "multipart/form-data")

    client := &http.Client{}
    resp, err := client.Do(req)
    if err != nil {
      panic(err)
    }
    defer resp.Body.Close()

    fmt.Println("response Status:", resp.Status)
    fmt.Println("response Headers:", resp.Header)
    body, _ := ioutil.ReadAll(resp.Body)
    fmt.Println("response Body:", string(body))
    fmt.Printf("%#v", c);
  }