It will be nice to use real example. It's not obvious from this example if you should specifiy string, `File`, `Pathname` or `Dir` instance.

Maybe you can use this as example taken from spec.

```ruby
ssl_client = Mysql2::Client.new(
  :sslkey => '/path/to/client-key.pem',
  :sslcert => '/path/to/client-cert.pem',
  :sslca => '/path/to/ca-cert.pem',
  :sslcapath => '/path/to/newcerts/',
  :sslcipher => 'DHE-RSA-AES256-SHA'
)
```