go toに marks the destination, and 行き is the stem of 行く (to go). It can connect to another verb or phrase, as in に行きたがっている (wants to go to) or に行き間に合った (went to and arrived in time).
JA: 週末に京都に行き、寺を見学した。
EN: I went to Kyoto over the weekend and visited a temple.