Use `gd` coc-definition jump into 3rd plugin showing Target of URI doesn't exist

It do well in flutter project, But display diagnostic error in 3rd party plugins like Provider after I used command `gd` (coc-definition) to jump into the source file.

```dart
import 'package:provider/provider.dart';
...
Provider.of(context, listen: false)
.setConversionList(conversationList);
```

**To Reproduce**
1. put cursor on `Provider`
2. press `gd` key
3. jump into file: "~/learn/flutter/soft/flutter/.pub-cache/hosted/pub.dartlang.org/provider-6.0.1/lib/src/provider.dart"
4. then error displayed

import 'package:collection/collection.dart'; >>> **Target of URI doesn't exist** ...

**Screenshots**

The following image is in my project, it is right!


The following image shows error after jump into provider.dart

**Desktop (please complete the following information):**
- OS: macOS Catalina
- Neovim: v0.6.1

**Output channel:**

1. Set `"flutter.trace.server": "verbose"`
2. Restart coc using `:CocRestart`
3. Reproduce the issue
4. `:CocCommand workspace.showOutput` open output list and select `flutter`

Paste Log from above:

```
[dev-command]: register dev command
[sdk]: No local fvm sdk
[sdk]: which flutter command => /Users/swot/learn/flutter/soft/flutter/bin/flutter
[sdk]: /Users/swot/learn/flutter/soft/flutter/version => 2.5.3
[sdk]: searchPaths: ~/snap/flutter/common/flutter
[sdk]: flutter command path => /Users/swot/learn/flutter/soft/flutter/bin/flutter
[sdk]: dart sdk home => /Users/swot/learn/flutter/soft/flutter/bin/cache/dart-sdk
[sdk]: analyzer path => /Users/swot/learn/flutter/soft/flutter/bin/cache/dart-sdk/bin/snapshots/analysis_server.dart.snapshot
[sdk]: dart command path => /Users/swot/learn/flutter/soft/flutter/bin/cache/dart-sdk/bin/dart
[fs]: executing command /Users/swot/learn/flutter/soft/flutter/bin/cache/dart-sdk/bin/dart --version
[sdk]: dart version: v2.14.4
[lsp-server]: rightVersion true
[lsp-server]: analysis server ready!
[lsp-closing-labels]: register closing labels
[daemon]: got message: {
"event": "daemon.connected",
"params": {
"version": "0.6.1",
"pid": 21029
}
}
[daemon]: got message: {
"event": "daemon.logMessage",
"params": {
"level": "status",
"message": "Starting device daemon..."
}
}
[daemon]: got message: {
"id": 1
}
[daemon]: Message without event
[daemon]: got message: {
"event": "device.added",
"params": {
"id": "emulator-5554",
"name": "sdk gphone x86",
"platform": "android-x86",
"emulator": true,
"category": "mobile",
"platformType": "android",
"ephemeral": true,
"emulatorId": "Pixel_2_API_30"
}
}
[daemon]: New device: sdk gphone x86
[daemon]: got message: {
"event": "device.added",
"params": {
"id": "chrome",
"name": "Chrome",
"platform": "web-javascript",
"emulator": false,
"category": "web",
"platformType": "web",
"ephemeral": false,
"emulatorId": null
}
}
[daemon]: New device: Chrome
```

I think whether the path settings right or not?

Please give me some advice, thanks a lot!

***
Some notes:

1. test in vscode: OK
2. test in Android Studio: OK
3. test in intelliJ IDEA CE: OK

The following image is in intellJ IDEA, it is OK!


The following operation took no effect:

```
"flutter.workspaceFolder.ignore": [
"/Users/swot/learn/flutter/soft/flutter/.pub-cache/hosted/pub.dartlang.org/",
"/Users/swot/learn/flutter/soft/flutter/.pub-cache/hosted/pub.dartlang.org/provider-6.0.1/",
"~/.pub-cache/"
]
```

flutter packages get