UPDATE: This is changed now and author wants that we install drupal launcher and then drupal console per project as stated here so composer global require is no longer supported
https://docs.drupalconsole.com/en/getting/project.html
To continue on installing globally vital drupal tools (http://drupaldump.com/install-composer-and-drush-globally)
You can install Drupal Console project globally using composer.
$ composer global require drupal/console:@stable
Add the binary directory to your class path:
$ echo "PATH=$PATH:~/.composer/vendor/bin" >> ~/.bash_profile
You can now execute console using:
$ drupal generate:module