As we all know, we need Drush8 for our Drupal8 development platform. I have tried installing Drush 8 using composer, but sometimes it turns out to be a disaster, especially when you try to install Drush 8 on the Digital Ocean Droplet having Ubuntu 16.04.
I have faced the same issue in the last few months to get the Drupal8 development platform ready with Drush8. So I have decided to find a solution to fix that forever. Well, finally found one which are the following lines of commands.
cd ~ php -r "readfile('http://files.drush.org/drush.phar');" > drush chmod +x drush sudo mv drush /usr/bin drush init
If you are still facing any issue, please leave a comment, We will help you out to get your platform ready with Drush8.