AKA Cheating.
Refs are currently powerless to do anything when goalkeepers are struck down by these dreadful injuries that they've suddenly started to experience. What can be done? The law that says a player who received treatment has to leave the pitch for 30 seconds now penalises the team where a player was genuinely hurt. But, it has cut down on the play acting by outfield players.
But the goalkeeper is immune from the 30 second on the sidelines for reasonable reasons. If the keeper genuinely required treatment, then left the field of play for 30 seconds, the team would be massively disadvantaged.
I'd change two things.
Firstly, an outfield player who requires treatment on the pitch. 30 seconds on the touchline. But, if the player who caused the injury receives a yellow card, they also leave the field of play for the same length of time. That way, the team that committed the foul don't get an advantage. If the action results in a blood injury, but was accidental, so no yellow card, the 'guilty' player still leaves the pitch while the blood injury is sorted out.
For an injured goalkeeper, they must be replaced by the substitute goalkeeper, but they can be swapped back, after one minute, the next time there was a break in play (so potentially, a few minutes). Yesterday's cheat would have needed to leave the pitch three or four times. He'd have come back on, but the disruption to Newport would have stopped the cheating. I'm sure no keeper would feign injury, if they knew they were going to be substituted.
The only exception would be, if the keeper had already been substituted, in which case, keep the same situation as it is now, but that would be very rare. As it is, we've seen multiple cases of cheating this season.