How can i pass username and password int http req

Question

Recently I have to make login to ubnt(UNifi) devices from flutter application

so I must pass user and password into URL

this is my code :

const url = 'http://10.66.5.8/login.cgi?uri=/';
var res = await http.post(Uri.parse(url), body: {
  'username': 'ubnt',
  'password': 's11n',
});

if (res.statusCode == 200) {
  if (await canLaunch(url)) {
    await launch(url);
  } else {
    throw 'Could not launch $url';
  }
} else {
  print(res.statusCode);
  ScaffoldMessenger.of(context)
      .showSnackBar(SnackBar(content: Text('Error')));
}

I try with API HTTP but no result