@mark_v3553 Currently in Go we don't support the previous configuration options around access from specific platforms.
But is part of our roadmap for next year.
You can achieve this using Custom Flows in SFDC.
I just a quick one and the key variable you need is 'LoginFlow_Platform'.
There is also 'LoginFlow_UserAgen' but there is quite a bit of data in that which you will need to parse.
Examples of flows are here:
I Used this video:https://www.youtube.com/watch?v=4lVgptJvehM
And you can check the device platform OS logging in.
Build your flow to either kick out if that variable is Android or challenge.. see below me using it on my iPhone.
No problem was a learning for me too