This Shield Guard Is Obviously Super Strong but Too Cautious

Lin Mo traveled through time. Opening his eyes, there was a silver-white buckler in his hand, and in front of him was a snarling slime. Good news: He has awakened his golden finger. Bad news: The golden finger is called [Absolute Guardian System], and the first task of the system is—— "Please take one attack. Reward: Shield Proficiency +1." Lin Mo:? ? ? … Okay, he admitted it. After all, the rules of this system are simple: Being beaten makes you stronger.