[WEB] Cannot read property 'Symbol(dartx.toUpperCase)' of null

final _sigV4S3Client = Sigv4Client(
      keyId: "ACCESS_KEY",
      accessKey: "SECRET_KEY",
      region: config.region,
      serviceName: "s3",
    );

    final Dio _dioClient = Dio();
    _dioClient.interceptors.add(LogInterceptor());

    final String url =
        "https://bucket-name.s3-eu-west-1.amazonaws.com/kitten-small.png";

    FilePickerResult result = await FilePicker.platform.pickFiles();
    PlatformFile file = result.files.single;

    var response = await _dioClient.put(
      url,
      options: RequestOptions(headers: {"Content-Type": "image/" + "png"})
          .sign(_sigV4S3Client),
      data: file.bytes,
    );

[+6467 ms] TypeError: Cannot read property 'Symbol(dartx.toUpperCase)' of null
                        at client.Sigv4Client.new.signedHeaders (http://localhost:54836/packages/sigv4/src/client.dart.lib.js:108:22)
                        at Object.DioExtension$124sign [as DioExtension|sign] (http://localhost:54836/packages/sigv4/src/extensions/http.dart.lib.js:50:25)
                        at putFile (http://localhost:54836/packages/multibook/features/library/data/api/s3/S3Api.dart.lib.js:67:100)
                        at putFile.next (<anonymous>)
                        at http://localhost:54836/dart_sdk.js:39029:33
                        at _RootZone.runUnary (http://localhost:54836/dart_sdk.js:38886:58)
                        at _FutureListener.thenAwait.handleValue (http://localhost:54836/dart_sdk.js:33872:29)
                        at handleValueCallback (http://localhost:54836/dart_sdk.js:34432:49)
                        at Function._propagateToListeners (http://localhost:54836/dart_sdk.js:34470:17)
                        at _Future.new.[_completeWithValue] (http://localhost:54836/dart_sdk.js:34312:23)
                        at async._AsyncCallbackEntry.new.callback (http://localhost:54836/dart_sdk.js:34335:35)
                        at Object._microtaskLoop (http://localhost:54836/dart_sdk.js:39173:13)
                        at _startMicrotaskLoop (http://localhost:54836/dart_sdk.js:39179:13)
                        at http://localhost:54836/dart_sdk.js:34686:9

 sigv4: ^4.1.1

Flutter 1.26.0-17.3.pre • channel beta • https://github.com/flutter/flutter.git
Framework • revision 4b50ca7f7f (2 weeks ago) • 2021-02-04 19:44:27 -0800      
Engine • revision 2c527d6c7e
Tools • Dart 2.12.0 (build 2.12.0-259.8.beta)

arnemolland / sigv4

[WEB] Cannot read property 'Symbol(dartx.toUpperCase)' of null #24