Let's create a new directory under pkg called "facebook" and write a NewMedia() function, and GetFeatures() method.

• NewMedia() should setup authentication to the Facebook API and return back a Media struct with a Facebook api client

• GetFeatures() should extract the necessary features from a Facebook profile and return a botdetector.Features type

Since the Facebook media struct has a GetFeatures() method, it satisfies the social media interface in pkg/social/social.go.
Modify in main.go the NewSocialMedia() function to return a social.Media() type which corresponds to the type of url passed in by the user. If its a twitter URL, call the twitter.NewMedia() function. If it is Facebook, call the facebook.NewMedia() function you created.

Have you looked into using the Twitter Labs API? They have multiple apis, one of them has elasticsearch like searching capabilities and much. Their labs team or research division has some interesting stuff.