If you only need the $PATH to be set in the integrated terminal, you can use VS Code's terminal.integrated.env.<platform> setting (added in version 1.15). Find the setting for your platform in the settings, click "Edit in settings.json", and add a "PATH" field like so:

"terminal.integrated.env.osx": {
  "PATH": "${env:PATH}:/my/path"
}

(Replace .osx with .linux or .windows as needed.)

The expression ${env:PATH} causes the existing contents of the $PATH environment variable to be inserted. This way you can extend it without hard-coding it.

As for having the $PATH available everwhere in VS Code, so that it will be used by extensions that call binaries, the only workaround I've found so far is this:

1. Configure your shell to have the $PATH you want. For example, I'm using Bash, and my ~/.bash_profile has the following line:

    PATH="$PATH:$HOME/bin"
   

2. In VS Code, press ⇧⌘P and type install 'code' command if you haven't done so before.

3. Quit VS Code.

4. Launch VS Code not by clicking its icon in the dock, but by opening Terminal.app and typing code. Your newly set path will be active in VS Code until you quit it.

5. If VS Code restarts, for example due to an upgrade, the $PATH will reset to the system default. In that case, quit VS Code and re-launch it by typing code.

Update: VS Code on Mac and Linux now apparently tries to automatically resolve the shell environment when it is started by clicking the icon (rather than via code). It does this by temporarily starting a shell and reading the environment variables. I haven't tested this though.

Assuming you mean for a debugging session(?) then you can include a env property in your launch configuration.

If you open the .vscode/launch.json file in your workspace or select Debug > Open Configurations then you should see a set of launch configurations for debugging your code. You can then add to it an env property with a dictionary of string:string.

Here is an example for an ASP.NET Core app from their standard web template setting the ASPNETCORE_ENVIRONMENT to Development :

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": ".NET Core Launch (web)",
      "type": "coreclr",
      "request": "launch",
      "preLaunchTask": "build",
      // If you have changed target frameworks, make sure to update the program path.
      "program": "${workspaceFolder}/bin/Debug/netcoreapp2.0/vscode-env.dll",
      "args": [],
      "cwd": "${workspaceFolder}",
      "stopAtEntry": false,
      "internalConsoleOptions": "openOnSessionStart",
      "launchBrowser": {
        "enabled": true,
        "args": "${auto-detect-url}",
        "windows": {
          "command": "cmd.exe",
          "args": "/C start ${auto-detect-url}"
        },
        "osx": {
          "command": "open"
        },
        "linux": {
          "command": "xdg-open"
        }
      },
      "env": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      },
      "sourceFileMap": {
        "/Views": "${workspaceFolder}/Views"
      }
    },
    {
      "name": ".NET Core Attach",
      "type": "coreclr",
      "request": "attach",
      "processId": "${command:pickProcess}"
    }
  ]
}