app.use(express.static(path.join(__dirname, 'public')));

project_root/
  node_modules/
  public/
    static/
       node_modules/ # symlinked directory

# symlink node_modules to public directory
rm -rf "${postinstall_pwd}/public/static/*"
rm -rf "${postinstall_pwd}/public/static/node_modules"
mkdir -p "${postinstall_pwd}/public/static"
ln -s "${postinstall_pwd}/node_modules" "${postinstall_pwd}/public/static"

app.use(express.static(path.join(__dirname, 'public')));
app.use(express.static(path.join(__dirname, 'node_modules')));