Datasource class could not be found

Let's say you defined a new connection example-connection in your config/app_local.php:

'example-connection' => [
    'host' => 'localhost',
    'username' => 'my_username',
    'password' => 'my_password',
    'database' => 'my_database_name',
    'url' => env('DATABASE_URL', null),
],

If you don't specify className and driver, you may be getting a MissingDatasourceException error.

[Cake\Datasource\Exception\MissingDatasourceException] Datasource class example-connection could not be found.

To fix, change your connection configuration to:

'example-connection' => [
    'className' => 'Cake\Database\Connection',
    'driver' => 'Cake\Database\Driver\Mysql',
    'host' => 'localhost',
    'username' => 'my_username',
    'password' => 'my_password',
    'database' => 'my_database_name',
    'url' => env('DATABASE_URL', null),
],