Fix function comments based on best practices from Effective Go

[CodeLingoBot]

Every exported function in a program should have a doc comment. The first sentence should be a summary that starts with the name being declared. From effective go.

PR generated by CodeLingo. Install here to drive Continuous Higher Standards.

[mullikine]

Hi russross and blackfriday contributers,

Shane from CodeLingo here. This PR is testing out a new service. I'd love to hear your feedback or answer your questions. We're keen to learn how we can best help dev teams without getting in your way.

Shane & the CodeLingo Team