Substitution with environment variables

[cecilphillip]

#1094 is closed, so I'm opening a new one here.
Variable substitution using ${env:var} doesn't seem to be working for me when I try to set it in the localPath property under volumes. I'm using version 1.3.1 on MacOS.
Predefined variables like ${workspaceFolder} work though.

Running the following task outputs the expected path.

 {
      "label": "echo",
      "type": "shell",
      "command": "echo ${env:HOME}"
 }

When I run the container using the extension, the docker run command contains -v "${env:HOME}/.aspnet/https:/https:ro" versus -v "/home/myuser/.aspnet/https:/https:ro"

my configured task looks like this..

{
      "type": "docker-run",
       "label": "docker-run: website debug",
       "dependsOn": [
             "docker-build: website debug"
         ],
         "dockerRun":  {
             "volumes": [
              {
                  "localPath": "${env:USER}/.aspnet/https",
                  "containerPath": "/https",
                  "permissions": "ro"
              }
             ]
            },
            "netCore": {
                "appProject": "${workspaceFolder}/src/ContosoCrafts.WebSite/ContosoCrafts.WebSite.csproj",
                "enableDebugging": true
            }
},

[bwateratmsft]

This one is the same as #1961, ultimately same as #1413. @cecilphillip, we need changes from the VSCode team to unblock this scenario, do you mind commenting on microsoft/vscode#81007 to encourage them to make said changes? 😄