Follow core routing files pattern key rename to path.

cron_example:

  pattern: 'examples/cron_example'

  path: 'examples/cron_example'

  defaults:

    _form: '\Drupal\cron_example\Forms\CronExampleForm'

  requirements:

# In order to create pages is necessary to define routes for them. The

# following lines defines three of them for this module.

page_example_description:

  pattern: 'examples/page_example'

  path: 'examples/page_example'

  defaults:

    _content: '\Drupal\page_example\Controller\PageExampleController::description'

  requirements:

# the menu system will first look for a route with that path. In this case it

# will find a match, and execute the _content callback.

page_example_simple:

  pattern: 'examples/page_example/simple'

  path: 'examples/page_example/simple'

  defaults:

    _content: '\Drupal\page_example\Controller\PageExampleController::simple'

  requirements:

# the function after the match, the function can do additional checking or

# make use of them before executing the callback function.

page_example_arguments:

  pattern: 'examples/page_example/arguments/{first}/{second}'

  path: 'examples/page_example/arguments/{first}/{second}'

  defaults:

    _content: '\Drupal\page_example\Controller\PageExampleController::arguments'

  requirements: