Cloning GitHub repository error "Fatal unable to access could not resolve host github.com"

I'm trying to clone a GitHub repository in Ubuntu Server VirtualBox using the sudo command "sudo git clone https://github.com/username/repositoryname.git" however I got a fatal error that says fatal:unable to access 'https://github.com/username/repositoryname.git/': Could not resolve host: github.com. How do I solve this?