vscode-extension-samples/proposed-api-sample/src/extension.ts

import * as vscode from 'vscode';

export function activate(context: vscode.ExtensionContext) {
	console.log('Congratulations, your extension "proposed-api-sample" is now active!');

	/**
	 * You can use proposed API here. `vscode.` should start auto complete
	 * Proposed API as defined in vscode.proposed.<proposalName>.d.ts.
	 */

	const disposable = vscode.commands.registerCommand('extension.helloWorld', () => {
		vscode.window.showInformationMessage('Hello World!');
	});

	context.subscriptions.push(disposable);
}