Ah, the joys of Go Around mode on a three-axis (ie no collective) autopilot where there is no speed protection. A certain recipe for unexpected death in an IFR go around for the unpracticed. The really annoying bit is that generally the go around mode is linked to vertical speed. So your left hand is not actually controlling the rate of climb but rather your airspeed. And naturally of course your focus at low altitude IMC is on the altimeter and not the airspeed. You see the initial pitch up from the GA and then you get onto other things and miss the speed washing off .
I personally teach (on a three axis system) that you've got four options (GA (lethal), ALT ACQUIRE (not much better), IAS and reverting to ATT). The latter seems the most natural (power directly related to going up) but IAS works the best overall for a 135 at least.
On the topic of workload in the go around, due to having access to a decent FMS/GPS (GTN750) I teach to use the GPS coupling for the missed approach and just wait until your in the (automated) hold before even thinking about what's next. Needs practice though