Update main.go

[ehsan-fmb]

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[ehsan-fmb]

hi.
i seprate connection part from handller in (join_to_database) function.can you check it?
i try to fix test cases in coming days.
and i have a question about number of connections to mongodb.with each request to server,number of that increases.is that a problem?
i tried to resolve it with "defer cancel()" but it didn't work.
can you help to do this?
and i ask again about access on iot platform for register nodes.and forgive me for that.