Casting a cantrip immediately after taking damage

I was wondering if there was any way to have the cantrip, "mending", take affect right after i take damage. My character has the construct tag, meaning that mending would actually heal him.

Ready action? 

The Mending spell doesn't heal constructs. It would say so if it did. A cantrip that can heal creatures would be extremely powerful.

Mending has a casting time of 1 minute so it's extremely unlikely to be of any use in combat.

If the casting time were 1 action, you could use the Ready action, but that requires concentration, so the damage might cause you to lose the spell.