I am trying to use environment variables within task in my tasks.json file of a C# project in vscode.
In my launch.json file I have this code to parse a .env file:
"configurations": [
  {
    ...
    "envFile": "${workspaceFolder}/.env",
  }
]
I then have in the tasks.json file this task:
{
  "label": "login",
  "command": "sh",
  "type": "shell",
  "args": [
    "${workspaceFolder}/etc/login.sh",
    "${env:USERNAME}",
    "${env:PASSWORD}"
  ]
}
This seems to be the code that's implied from https://code.visualstudio.com/docs/editor/tasks, however (from testing by echoing in another task) I have found these last two args to be blank. After researching online I think I have found the reason, the configurations..env is used by the tasks themselves rather than being accessible by task.json that run and so can't be accessed. 
How do I create (use) these env variables within the tasks.json?
 
     
    