What should I write to my boss if I want to send a text message to say goodbye?

It is better to say hello in person, which is more formal and polite.

You can find an excuse, such as the work handover plan before leaving your job, let him have a look, ask for his advice, and at the same time show them a gesture, the main purpose is to reassure the leaders. The attitude at this time will make the leaders feel that you are broad-minded. If you have the opportunity to work together again in the future, they will definitely regard you with special respect. After the handover, you should record the handover process, send it to the leader and copy it to the colleague who took over your work, and kindly introduce the colleague who took over your work to the person who cooperated with you on the project.

Say some simple pleasantries when saying goodbye, thank the leaders for their training, explain what they have learned in the company, and then ask the company leaders to make some suggestions, giving people the feeling that they must be particularly sincere.