Godsend triggers after blockers are declared but before combat damage, so you get to exile the blocker before damage is assigned.

How does godsend work MTG?

A question the Godsend says; Whenever the equipped creature blocks or is blocked by one or more creatures, you can exile one of these creatures. Godsend's ability triggers when blockers are declared in the Declare Blockers Step, and it will resolve on that same step, so it always happens before the Combat Damage Step.

Does exile deal damage?

-5: Deals damage to target creature equal to the total number of instant and sorcery cards you own in exile and in your graveyard.