function regen()
    for _,player in pairs(minetest.get_connected_players()) do
        local anim = default.player_get_animation(player)
        if player:get_hp() < 20 and anim.animation == "sit" then
            player:set_hp(player:get_hp()+1)
        end
    end
end

minetest.after(5,regen)