flutter swift does not pick environment variable from vscode launch

I try to pass an environment variable from vscode to the swift file in flutter but seems like the swift file cannot pick it.

The launch file I am using for vscode

{
            "name": "myapp (debug alpha)",
            "request": "launch",
            "type": "dart",
            "flutterMode": "debug",
            "args": [
                "--flavor",
                "alpha",
                "--dart-define",
                "environment=alpha"
              ],
              "env": {
                "MARKETING_VERSION": "1.0.0",
                "GOOGLE_MAP_API_KEY": "xxxxxx"
              }     
        },

The code in AppDelegate.swift is

if let googleMapApiKey = ProcessInfo.processInfo.environment["GOOGLE_MAP_API_KEY"] {
        GMSServices.provideAPIKey(googleMapApiKey)
    }

When I run my app by running the launch, it exits immediately when the google map is launched. Then I directly run GMSServices.provideAPIKey(xxx) and the google map can be launched. So I guess the GOOGLE_MAP_API_KEY is not picked from the environment.

Can anyone please help on it? Thank you