There's nothing to panic if a user close voted your question. Lets assume that he close voted unknowingly or say he is not sure of how to use his privileges so whats the best you can do is post a comment to the user saying that the question may be related but not duplicate so please retract your close vote.
If the user doesn't retract his close vote, then the vote will expire at certain point automatically by the system (I'll share a link for this feature soon). Am sure you must be seeing a notice above your question explaining that you might find answers on X question but its only visible to you and not others.
For some reason if your questions gets closed, and you think it was not fair, feel free to flag your question and ask for moderators help, we will reopen your post if the close votes are not justified.
Also, it takes 5 votes for the users to close your question, so if other users are wise enough to judge that the question is not a duplicate, they will not cast a close vote.
Note: The user is not a moderator, there are only three
moderators on the site. If a moderator casts a close vote, it
will close your question immediately. The user is having privileges
to cast close and reopen votes.