Follow up with the employer
If you developed a good relationship with someone during your internship you are more than welcome to continue on with a mentorship with them, providing that employer is fine with it. Let your employer know if you have moved on to another job and keep them updated. They may know of future job opportunities and contact you later on for a permanent position upon graduation.
Thank the employer
Remember to thank the employer for providing a valuable learning opportunity and memorable experience. You can thank them personally on your last day on the job,send them a thank you note, or email no more than a week after you have finished work. Do ask if they would be a reference for you. A year will go by fast and to have that reference will be valuable. Be sure when you use them as a reference to call before you interview that they are still willing to be a reference for you. Employers may move on or change roles so it is good practice to make sure they are up to date and have current information for your future employers.