token might not be set by the time it invokes http.get. Change it to
String token = await Candidate().getToken();
final response = await http.get(url, headers: {
'Content-Type': 'application/json',
'Accept': 'application/json',
'Authorization': 'Bearer $token',
});
print('Token : ${token}');
print(response);
So that it is for sure set with right value.