It depends on the software (CPIP) update is installed.
Prior to around MSN 4400, the standard was that on go-around, the lateral guidance automatically engaged in 'GA TRK' (go around track). This is the track that the aircraft was following at the time of the go-around (so may, or may not be correct in terms of runway track). The go around track will then be followed ad infinitum until another lateral mode is engaged (i.e. NAV or HDG). The FMA in this case will annunciate MAN TOGA|SRS|GA TRK.
With the latest software (or standard on newer aeroplanes ie. MSN 4400-ish onwards), the lateral mode will be NAV. As it suggests, the AP will follow the missed approach that is coded in the navigation database. Which will of course have been checked for accuracy prior to, or during the briefing phase. The FMA in this case will annunciate MAN TOGA|SRS|NAV.
Hope this helps.