Goetia or Ars Goetia is the practice of conjuring demons described in the first part of The Lesser Key of Salomon, a 17th century book of spells on demonology.
The word goetia or goëtia, as it was originally spelled originates from the Ancient Greek word goēteía, meaning "sorcery", and was then transcribed to its Latin form, goëtia. In the the 16th century, it was transcribed to English as goety, but is predominantly used in the Latin form, goetia.
The correct pronunciation of goetia is goh-eh-tee-ah. Pronunciation of Latin words, especially those taken from Greek that weren't used by the Roman, are difficult to trace, and this is the case with goetia. As a consequence, many people pronounce goetia as go-eh-sha, but this is probably a pronunciation based on how the sequence "tia" is usually pronounced in English. The pronunciation of the "tia" sequence in Classical Latin is tee-ahm, for example in the word etiam, which is pronounced eh-tee-ahm. This differs from Ecclesiastical Latin, which pronounces "tia" as tsee-ah. If we are to follow the route of Classical Latin, then the pronunciation of goetia is goh-eh-tee-ah. In any case, this excludes that goetia is pronounced as goh-eh-sha.