It can be a good idea to hang out with your co-workers or colleagues during your spare time, but it is crucial to have a boundary for this relationship.
You are in touch with your colleagues as much as enough during the workdays, so it is not logical and reasonable to go for a dinner with them, or joining each other to go to a gym or party, to name but a few. There should be a red line for the time you are spending with your co-workers, because it can have some terrible effects on your productivity and job safety at work. For example, if you think your colleague is a sensitive and sympathetic person, admittedly you are not allowed to have a friendly conversation with them, and talk about every secrets of your own life in detail, because there is not any commitment that shown they can be reliable all the time.
On the other hand, your fellow workers could not keep their word, and it is absolutely possible to transfer your words to the manager, and even it would lead you to be fired. despite of it is normal to be in contact with your colleagues at work to share your ideas, and co-operate with each other to have a presentation, and be prepared for sessions, but there is not any necessity to share your experiences out of work atmosphere.
In conclusion, every employed person should keep his/her working life completely far from his/her private life. It helps people to have a better work-life balance, and contributes to aquire better job positions, and obtain more happier social life.