Question: I tried to run `flutter pub get` and I got this error:

```
Error on line 1, column 1 of pubspec.lock: Unexpected character
╷

1 │
│ ^

  ╵
pub upgrade failed (65;   ╵)

```

Answer: 
The file pubspec.lock is a generated file, so you can delete it and then regenerate it.

Delete **pubspec.lock**.

Run the following command:

```
flutter pub get

```

or

```
flutter pub upgrade

```

Notes on [pub upgrade](https://dart.dev/tools/pub/cmd/pub-upgrade) (you could probably skip the delete step).
Delete the file at flutter/packages/flutter\_tools/pubspec.lock then try flutter pub upgrade again.

You may have interrupted the upgrade process before it finished hence the file became invalid.