I learned from Americans that "go out with" is a grey area expression for "hang out with" of having not serious relationship and "dating" of serious relationship between male and female. Is it true?
Can it be either "hang out with" and "date" depending on situation?
Expressions used can vary among age groups and socioeconomic classes.
I would think if you are "going out" with someone that is the same as dating.
Whether it is "exclusive" or not is another question.
When I was in middle and high school. if a couple were together exclusively, we would say they were "going together" or that "Sue is going with Bob."
Who knows what the kids say today.
It can mean both depending on context. "Going out with" as a relationship status wouldn't be used in the same way as "going out with" as a simple activity with another person.
What are you doing tonight?
I'm going out with Dave = I will be spending the evening with Dave. This says nothing about your personal relationship with Dave.
Are you single?
No. I'm going out with Dave = I'm currently dating Dave. This is definitely a statement about your personal relationship.