Xamarin.Forms - Custom Logic For Enabling/Disabling iOS "Go" Key?

I'm using Xamarin.Forms to build a login page. For the password field, I've set the Control.ReturnKeyType to UIReturnKeyType.Go ("Go" key). The default behavior is that if any character is entered into the field, the "Go" key is enabled. But I want to keep the "Go" key disabled if there are only spaces in the field. Is there a way to add custom logic for the enabling/disabling of the "Go" key?

Note: I realize that disallowing spaces in the field is one solution, but I need to allow spaces.

iOS SDK does not have a way to programmatically enable or disable GO button based on some condition.