Is Mr. S. N. Goenka's Vipassana Meditation a Buddhist tradition? It appeared that most students learning Buddhism will automatically assume Vipassana Meditation taught by Mr. S. N. Goenka synonymous with Buddhist meditation, methods taught by the Buddha, is it so?  

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Remark Added 15/03/2017

The knowledgeable Suminda (@Suminda Sirinath S. Dharmasena) pointed to an article which attempted to establish the "U Ba Khin Vipassana method told by Mr. Goenka" its connection with Mahayana (of the Chinese Lineage), this should definitely be refuted. Mr. Goenka himself with his entire Insight Movement is completely unrelated to the Mahayanist teaching. 

In the article Ven. Analayo wisely drew inspiration from the Mahayanist Sutra however, it's uncertain under what circumstance someone provided him an incorrectly translated work: 


  念諸息遍身, 亦念息出入, 悉觀身中諸出息入息, 覺知遍至身中乃
  至足指遍諸毛孔, 如水入沙, 息出覺知從足至髮遍諸毛孔亦, 如水
  入沙.


Mindfulness [during] all breaths pervades the body, [while] being as
well mindful of the out- and in-breaths. Completely contemplating the
inside of the body [during] all out-breaths and in-breaths, awareness
pervades and reaches inside the body up to the toes and the fingers
and pervades every pore [on the surface of the body], just like water
entering sand, aware from the feet to the hair [while] breathing out
[and in], pervading every pore as well, just like water entering sand.


This should read as (translation is mine): 


  Set the mind to all the breaths be aware of their permeating the whole
  body (念諸息遍身). Also be mindful of the breath going-out and going-in
  (亦念息出入). Thoroughly observe all the out-going and in-going breaths
  inside the body (悉觀身中諸出息入息), be conscious of their permeating from
  inside the body unto the toes and fingers even pervading all the
  pores, as if water entering sands (覺知遍至身中乃至足指遍諸毛孔, 如水入沙). [When]
  breath going-out, be conscious of it from feet unto the hairs
  pervading all the pores, also as if water entering sands
  (息出覺知從足至髮遍諸毛孔, 亦如水入沙).


It definitely has nothing to do with Mr. Goenka's "body-scanning" technique.

Here breath 息 is not simply the air coming in-out the nose-mouth that we do in breathing. Ānāpānasmṛti (Pali: Ānāpānasati) meditation taught by most of the general media is incorrect. There are at least 3 stages: counting, following, stillness; progressed gradually.
Goenka tradition seems to be most close to meditation instruction sourced directly from the Suttas. A course is divided into  parts:


Anapana - cultivation of Samadhis (1/3 of the length of the course)
Vipassana - cultivation of Panna (slightly less than 1/3 of the lenth of the course)
Metta - (1 or 2 days depending on the length of the course.)


Anapana closely follows that of the [Maha] Satipatthana / Kayagatasati Suttas.

In the Vipassana part, the main instruction is whatever the sensation contemplate its impermanence and be equanimous towards it. 


  Having fully understood all things, he knows whatever feelings there are, whether pleasant, painful
  or neither painful nor pleasant.
  
  As regards to those feelings,
  
  he dwells contemplating impermanence in them;
  
  he dwells contemplating dispassion [fading away of lust] in them;
  
  he dwells contemplating ending (of suffering) in them;
  
  he dwells contemplating letting go (of defilements).
  
  When he dwells contemplating impermanence in them, contemplating dispassion in them, contemplating
  ending in them, contemplating letting go,
  he does not cling to anything in the world.
  
  Not clinging, he is not agitated; being not agitated, he himself surely attains nirvana.
  
  He understands,
  "Birth is destroyed, the holy life has been lived, done what is to be done, there is no more for this state
  of being."


Pacalā Sutta

Similarly there many more Suttas which similar instructions re occur throughout the whole cannon. E.g.: Pahāna Sutta, Avijja Pahana Sutta 2, Dīgha,nakha Sutta, Sal,āyatana Vibhanga Sutta, Indriya Bhāvanā Sutta, Dhātu Vibhaṅga Sutta, Titth’ayatana Sutta


  Bhikshus, just as if a man were sitting covered from head to foot with a white cloth, so that there
  would be no part of his body to which the white cloth did not extend; even so, the monk sits, permeating
  the body with a pure, bright mind. There is no part of his entire body that is not pervaded by pure, bright
  mind. 


Kaya,gatā,sati Sutta

also


  so, too, a monk reviews this very body, wrapped in skin and full of various impurities, from the
  soles of the feet upwards and from the crown of the head downwards


Kaya,gatā,sati Sutta, Sati’patthāna Sutta


  As below, so above [upwards from the soles of the feet, and downwards from the tips of the hairs.]


Iddhi,pāda Vibhanga Sutta

This is similar in tone to the head to foot scanning technique.

In Buddhism, common term is letting go. The Suttas on Letting Go sheds more light on how to do it. They are: Pahāna Sutta and Avijja Pahana Sutta 2. This is the exact way that is being taught by S.N.Goenka.

Also an interesting read might be: The Ancient Roots of the U Ba Khin
Vipassanā Meditation by Ven. Analayo, which quotes some parallel in the Mahayana Tradition which you (@Bhumishu 米殊) are from I believe.

Instead of intellectually debating on whether the course is this or that why not take the course and clear you doubts. You can apply through: http://www.dhamma.org/en/index and course are conducted in many centres around the world. You can choose a location convenient to you.

What matters if the techniques works for you or not than is it this or that. So best is just try it.