I want to know the difference nuance between "going to" and "about to" in native English speaker's environment, which one is better to use or widely used?
Going to simply means intending to do something, at some point in the future. It can also imply (depending on context and speaker's tone of voice) that the intention is to do it 'sometime… never', i.e. the intention is very weak.
About to adds more immediacy to the intention of doing that thing; 'on the brink of doing something'. Or it can mean that the intention was interrupted (and possibly not fulfilled) by something else. It is often prefaced with just, which amplifies the immediacy.
"He was going to add another column to the spreadsheet" (but I'm not sure if he did so).
"I was about to make myself a cup of tea when the phone rang."
"Have you given Mum her medicine today?"
- "No, I was just about to."
The expression "about to" is used to indicate that something is imminent. In other words, something may happen so soon in the future that there should be no delay in preparing for it. We are right at the edge of the event, with little or nothing separating us from its occurrence. It might not be certain, however, that the event will actually occur.
The expression "going to" means that a process has begun that will definitely lead to a particular outcome. The timing of the outcome is not specified and has lesser importance than its definiteness.
If your spouse tells you: "it's going to rain" as you leave your home in the morning, he or she means that that there is some evidence or information that means rain is certain to result. Your next thought might be, "I wonder if I need to bring an umbrella along or whether I can make it to work before the rain comes." If your spouse says, "it's about to rain," your next thought might be: "Oh, I guess I am going to get wet unless I bring my umbrella or take immediate cover."
If you say: "those two countries are about to go to war," you mean that war may come at any time without further warning or that the slightest additional incident may cause it. There may even be time for a settlement that might make peace possible, but they are really very close to war. If you say: "those countries are going to war," you are saying that you are aware that circumstances have been set in motion that make a future war certain to happen.
"About to" can be ambiguous as to certainty. "Going to" can be ambiguous as to immediacy.
Consider the phrase "I am going to quit." The most likely meaning is that you have taken a decision to quit. Your decision means that a process leading to your quitting has begun, but the timing is unspecified. Said to a colleague just outside your boss's closed door, the phrase implies that in a few moments you will enter you boss's office and present your resignation, rather than sometime in the indefinite future. In this case the process leading to a definite result is not your decision, but rather your presence outside the door.
--The sun is going to stop shining in a few billion years.
--What leads you to make that prediction?
--I know that the sun needs hydrogen or helium fuel in order to shine, and it's fuel is limited.
Consider the phrase: "I am about to quit." The most common usage is probably to indicate that you are so unhappy with your job that the slightest provocation will lead you to quit. You have not made a final decision, but are really close to one. Said to a colleague outside your bosses door, this phrase implies that you will enter and present your resignation before going anywhere else or doing anything else.