Can you cancel a personal loan within 24hrs of signing contract?

This may be a state-specific question. On the federal level, there is a law called the Truth in Lending Act. For consumer-purpose loans that are secured by borrower's primary residence, the borrower must be given 3 business days to cancel the transaction.

You ask about "personal loan" which can mean different things to different people. I interpret personal loan to mean an unsecured, or "signature" loan. I am not aware of any law that permits someone to cancel a personal loan within 24 hours. Again this may be state-specific.