Dart Future HttpCLientRequest Returns Null - json

Question

The class Requests set up an HttpClientRequest. The method getTeamsJsonForRequest is supposed to return the JSON response. However, the variable 'return' is not being assigned properly I assum. The print 'CONTS' in the .then response successfully prints the correct response, but printing 'myres' sections says result is null. Not sure why result is not being assigned in the response.transform section.
class Requests {
static Future getTeamsJsonForRequest(String reqPath) async{
var result;
HttpClient myhttp = new HttpClient();
String path = '/api/v3' + reqPath;
myhttp.get('www.thebluealliance.com', 80, path)
.then((HttpClientRequest request) {
request.headers.set("accept", "application/json");
request.headers.set("X-TBA-Auth-Key", "XXXXX");
return request.close();
})
.then((HttpClientResponse response) {
response.transform(utf8.decoder).transform(json.decoder).listen((conts) {
print('CONTS: ' + conts.toString());
result = json.decode(conts).toString();
});
});
print('myres: ' + result.toString());
return result;
}
}

Answer 1

Short answer: avoid using Future.then inside an async method.
Your print is executing before the response comes back. https://www.dartlang.org/tutorials/language/futures#async-await
Without an await any work that is done asynchronously will happen after subsequent statements in this function are executed.
Here is how I'd write this:
Future<String> teamsJsonForRequest(String requestPath) async {
var client = new HttpClient();
var path = '/api/v3$requestPath';
var request = (await client.get('www.thebluealliance.com', 80, path))
..headers.set("accept", "application/json")
..headers.set("X-TBA-Auth-Key", "XXXXX");
var response = await request.close();
var result =
await response.transform(utf8.decoder).transform(json.decoder).single;
print('myres: $result');
return result;
}