You are missing one argument. As mentioned in the documentation, fs.cp is an asynchronous function that takes in a callback function

the final arguement needs to be a callback function

fs.cp('D:\\Developer\\insomniac-beta\\template', dir_path, (err)=>{ 
// handle error
})

It seems like you're using the promises API, but you didn't show how you import the module. Here's an example with the current Node LTS (v16.x):

Ref: fsPromises.cp(src, dest[, options])

import {promises as fs} from 'fs';

// ...

await fs.cp(sourceDir, destDir, {recursive: true});

Here's a full, self-contained example which creates a sample dir structure, copies it, verifies the copy, and cleans up the sample data:

example.mjs:

import * as path from 'path';
import {constants as fsConstants, promises as fs} from 'fs';
import {fileURLToPath} from 'url';
import {ok as assert} from 'assert/strict';

// Create sample folder structure, return relative file paths
async function createSampleFiles (rootDir) {
  const writeFileOpts = {encoding: 'utf8'};
  const filePaths = [];

  await fs.mkdir(rootDir, {recursive: true});

  let fPath = 'hello.txt';
  filePaths.push(fPath);
  fPath = path.join(rootDir, fPath);
  let text = 'hello world\n';
  await fs.writeFile(fPath, text, writeFileOpts);

  let dir = 'more';
  await fs.mkdir(path.join(rootDir, dir), {recursive: true});

  fPath = path.join(dir, 'wow.txt');
  filePaths.push(fPath);
  fPath = path.join(rootDir, fPath);
  text = 'wow\n';
  await fs.writeFile(fPath, text, writeFileOpts);

  return filePaths;
}

async function fsEntryExists (filePath) {
  try {
    await fs.access(filePath, fsConstants.F_OK);
    return true;
  }
  catch (ex) {
    if (ex instanceof Error && ex.code === 'ENOENT') return false;
    throw ex;
  }
}

async function assertFSEntryExists (filePath) {
  assert(await fsEntryExists(filePath), `FS entry not found for "${filePath}"`);
}

async function main () {
  const moduleDir = path.dirname(fileURLToPath(import.meta.url));

  const sourceDir = path.join(moduleDir, 'data');
  const destDir = path.join(moduleDir, 'data-copy');

  const relativePaths = await createSampleFiles(sourceDir);

  await fs.cp(sourceDir, destDir, {recursive: true});

  let exitCode = 0;

  try {
    const filePaths = relativePaths.map(fPath => path.join(destDir, fPath));
    for (const fPath of filePaths) await assertFSEntryExists(fPath);
    console.log('Copy successful');
  }
  catch {
    console.error('Copy failed');
    exitCode = 1;
  }
  finally {
    // Cleanup
    for (const dir of [sourceDir, destDir]) {
      if (await fsEntryExists(dir)) await fs.rm(dir, {recursive: true});
    }

    process.exit(exitCode);
  }
}

main();

$ node --version
v16.15.0

$ node example.mjs
Copy successful