The Collaborative International Dictionary of English v.0.48:

Go \Go\, n.
   1. Act; working; operation. [Obs.]
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            So gracious were the goes of marriage. --Marston.
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   2. A circumstance or occurrence; an incident. [Slang]
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            This is a pretty go.                  --Dickens.
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   3. The fashion or mode; as, quite the go. [Colloq.]
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   4. Noisy merriment; as, a high go. [Colloq.]
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   5. A glass of spirits. [Slang]
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   6. Power of going or doing; energy; vitality; perseverance;
      push; as, there is no go in him. [Colloq.]
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   7. (Cribbage) That condition in the course of the game when a
      player can not lay down a card which will not carry the
      aggregate count above thirty-one.
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   8. Something that goes or is successful; a success; as, he
      made a go of it; also, an agreement.

            "Well," said Fleming, "is it a go?"   --Bret Harte.
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   Great go, Little go, the final and the preliminary
      examinations for a degree. [Slang, Eng. Univ.]

   No go, a failure; a fiasco. [Slang] --Thackeray.

   On the go, moving about; unsettled. [Colloq.]
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WordNet (r) 3.0 (2006):

on the go
    adj 1: (of a person) very busy and active; "is always on the go"

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "on the go":
   astir, at it, at work, busy, employed, en route, engaged,
   full of business, hard at it, hard at work, in harness, in motion,
   in transit, occupied, on duty, on the bum, on the gad, on the hop,
   on the job, on the jump, on the move, on the road, on the run,
   on the tramp, on the wing, tied up, under sail, under way,
   working