This is an obviously correct sentence, what for being antiquated. It being ignored and left unadopted as if it were a mistake isn't right.

Seriously, one does not need to be a native to check that this pattern is valid although definitely antiquated.

What's antiquated about it? 😕

Perhaps not yet but "don't need" is gradually overtaking / taking over. Makes sense given the murkiness of semi-modal verbs (you won't say "need go" anyway, only "need to go").

@Ooneykcall

> one does not need to be a native to check that this pattern is valid although definitely antiquated.

I'm a native speaker. It's not antiquated.

> you won't say "need go" anyway, only "need to go"

That's an unhelpful comparison.

No one I know says "need go". I've never heard it and, honestly, I can't ever remember hearing it or reading it.
"Need not" is formal, for which reason you won't hear it often. In fact, you probably won't ever hear it spoken as such in the UK.
"Needn't" is still common in the UK. It might not be as common as 'don't need', but it's not antiquated, either. I say it interchangeably with "don't need".

EDIT:

I found this in Fowler's Modern English Usage (3rd edition, 1996, p.516):
"Used as a modal auxiliary, [need] can only be used in negative or interrogative constructions, or in phrases with a negative implication, e.g. *he needn't leave; need we leave?; needn't we leave now?; I need hardly say*."

In other words, "you needn't answer the letter" is fine, but "you need answer the letter" isn't.

Other examples it lists:

"The landlady need never know." – J. Frame, 1985
"But need she lie? Was he just a boy?" – M. Leland, 1985
"Nothing that need embarrass you. Not at this stage." – A. Lejeune, 1986
"You needn't bother to let me know." – C. Rumens, 1987

How English Works (Michael Swan & Catherine Walter, 1997, p.126) says:

"*Need* can sometimes be used like a modal verb (questions and negatives without *do*), especially to say what is (not) necessary at the time of speaking:

Do I need to pay now? OR Need I pay now?
He doesn't need to go. OR He needn't go.

[...]

Compare *didn't need to* and *needn't have*:

We didn't need to hurry; we had lots of time.
(It was unnecessary to hurry.)
We needn't have hurried – we got there much too early.
(It was unnecessary to hurry, but we did.)"

The Oxford Guide to English Usage (2nd edition, 1993, p.201), says:

"*Need* can be used like an auxiliary verb in the present tense in negative and interrogative sentences. This means that:

a) The third person singular does not add -s [...]
b) For the negative, *need not* replaces *does not need* [...]
c) For the interrogative, *need I (you, etc.) replaces *do I need* [...]
d) The bare infinitive follows instead of the *to-*infinitive."

I need to clarify what I said above: you can't have "need go" when the sentence is indicative, but you *can* have it when the sense is negative or interrogative. You can have it in a sentences like:

I don't know whether I need go or not.

But this would be less likely than *need to go* or when the bare infinitive is 'be':

I'll go if need be.