Learn a word a day - Go-to person/guy

Do you know that learning a word a day is similar to the way you take a tablet of Vitamin as the daily supplement?

A go-to person (slang) is someone who can be trusted to provide a specific service or deal with a particular problem. S/he is considered as a valued adviser. For example, Dara is the only go-to person for every IT technical issue in his company.