curl --header 'Expect: ' -F username=your_username_here
                         -F password=your_password_here
                         -F proxy='{"proxy": "http://user:password@127.0.0.1:1234","proxytype": "HTTP"}'
                         http://testapi.com/api/xoxo

const proxy = JSON.stringify({
        proxy: this.proxy,
        proxytype: 'HTTP',
    });

    const data = new FormData();
    data.append('username', config.username);
    data.append('password', config.password);
    data.append('proxy', proxy);

    try {
        const captcha = await axios.post(
            'http://testapi.com/api/xoxo',
            data,
            { headers: { 'Content-Type': 'multipart/form-data' } }
        );
        console.log(response);
    } catch (err) {
        console.log(err.response);
    }