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MINOR: [Go] Fix Flakey TestRowsPrematureCloseDuringNextLoop Test (#43804)



### Rationale for this change

Fixes a race condition in rows initialization that has been causing intermittent test failures.

### What changes are included in this PR?

Split query and init context. Update test to check for failure _after_ reading rows.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.

Authored-by: Joel Lubinitsky <joellubi@gmail.com>
Signed-off-by: Joel Lubinitsky <joellubi@gmail.com>