title: Couldn't use members from imported packages (Flutter)
body: <p>When trying to add 'http' and 'async' libraries to my project, it looks like the import was made right, but I cannot use the classes from imported packages.</p>
  
  <pre><code>import 'package:flutter/material.dart';
  import 'package:http/http.dart';
  import 'package:async/async.dart';
  </code></pre>
  
  <p>My code is:    </p>
  
  <pre><code>const request= "https://api.hgbrasil.com/finance/taxes?format=json&amp;key=";
  
  void main(){
  
    http.Response response = await http.get(request);
  
    runApp(MaterialApp(
      home: Container(),
  
    ));
  }
  </code></pre>
  
  <p>and I'm getting this errors when trying to run the app:</p>
  
  <pre><code>Compiler message:
  lib/main.dart:10:28: Error: Unexpected token 'await'.
    http.Response response = await http.get(request);
                             ^^^^^
  lib/main.dart:10:34: Error: Getter not found: 'http'.
    http.Response response = await http.get(request);
                                   ^^^^
  lib/main.dart:10:3: Error: 'http.Response' can't be used as a type because 'http' isn't defined.
    http.Response response = await http.get(request);
    ^^^^^^^^^^^^^
  Compiler failed on /home/alexandre/dev/flutter/conversor_moedas/lib/main.dart
  Finished with error: Gradle task assembleDebug failed with exit code 1
  </code></pre>
  
  <p>I've added the dependency in pubspec.yaml and did a packages get:</p>
  
  <pre><code>name: conversor_moedas
  description: A new Flutter application.
  
  # The following defines the version and build number for your application.
  # A version number is three numbers separated by dots, like 1.2.43
  # followed by an optional build number separated by a +.
  # Both the version and the builder number may be overridden in flutter
  # build by specifying --build-name and --build-number, respectively.
  # Read more about versioning at semver.org.
  version: 1.0.0+1
  
  environment:
    sdk: "&gt;=2.0.0-dev.68.0 &lt;3.0.0"
  
  dependencies:
    flutter:
      sdk: flutter
    http: ^0.12.0
  
    # The following adds the Cupertino Icons font to your application.
    # Use with the CupertinoIcons class for iOS style icons.
    cupertino_icons: ^0.1.2
  
  dev_dependencies:
    flutter_test:
      sdk: flutter
  
  
  # For information on the generic Dart part of this file, see the
  # following page: https://www.dartlang.org/tools/pub/pubspec
  
  # The following section is specific to Flutter.
  flutter:
  
    # The following line ensures that the Material Icons font is
    # included with your application, so that you can use the icons in
    # the material Icons class.
    uses-material-design: true
  
    # To add assets to your application, add an assets section, like this:
    # assets:
    #  - images/a_dot_burr.jpeg
    #  - images/a_dot_ham.jpeg
  
    # An image asset can refer to one or more resolution-specific "variants", see
    # https://flutter.io/assets-and-images/#resolution-aware.
  
    # For details regarding adding assets from package dependencies, see
    # https://flutter.io/assets-and-images/#from-packages
  
    # To add custom fonts to your application, add a fonts section here,
    # in this "flutter" section. Each entry in this list should have a
    # "family" key with the font family name, and a "fonts" key with a
    # list giving the asset and other descriptors for the font. For
    # example:
    # fonts:
    #   - family: Schyler
    #     fonts:
    #       - asset: fonts/Schyler-Regular.ttf
    #       - asset: fonts/Schyler-Italic.ttf
    #         style: italic
    #   - family: Trajan Pro
    #     fonts:
    #       - asset: fonts/TrajanPro.ttf
    #       - asset: fonts/TrajanPro_Bold.ttf
    #         weight: 700
    #
    # For details regarding fonts from package dependencies,
    # see https://flutter.io/custom-fonts/#from-packages
  </code></pre>
  
  <p>After that, IDE recognizes the packages in import but I cannot use it, as you can see in the image, the IDE recognizes <code>import 'package:http/http.dart';</code> but there is a error in the line <code>http.Response response = await http.get(request);</code></p>
  
  <p><a href="https://i.stack.imgur.com/tDzCd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/tDzCd.png" alt="enter image description here"></a></p>
  
  <p>As you can see, the library is there:</p>
  
  <p><a href="https://i.stack.imgur.com/pxFy0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/pxFy0.png" alt="enter image description here"></a></p>
  
  <p>I also tried "invalidate caches/restart" in Android Studio, but no success... The IDE version is: </p>
  
  <pre><code>Android Studio 3.2.1
  Build #AI-181.5540.7.32.5056338, built on October 8, 2018
  JRE: 1.8.0_152-release-1136-b06 amd64
  JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
  Linux 4.15.0-39-generic
  </code></pre>