You can do that via the Web Server configuration files.

If using Apache, you would need to add this to your configuration setup:

ServerName domain.com

If using Nginx, you would need to add this to your configuration setup:

server_name domain.com

Please remember you would need to restart the Web Server after making such changes. For more information on setting that up, you might want to read our guides on Setting up Apache VirtualHosts and Setting up Nginx Server Blocks.

Also please note if you are using a CMS, such as WordPress or Magento, you would need to edit the database entries that determine the site/home URLs. You can normally do this via the CMS admin panel, or directly via MySQL.

Hope it helps!
Jason Colyer
DigitalOcean Platform Support Lead

With NGINX, you can edit nginx configuration file
add this code
server {
listen 80;
servername yourdomain.com;
301 redirect http://yourdomain.com$requesturi;

}