-----Original Message-----
>From: Burak Serdar <bser...@ieee.org>
>Sent: Jul 22, 2019 11:13 AM
>To: Tong Sun <suntong...@gmail.com>
>Cc: golang-nuts <golang-nuts@googlegroups.com>
>Subject: Re: [go-nuts] Variable life time -- sql.DB connection defer closing
>question
>
>On Mon, Jul 22, 2019 at 9:35 AM Tong Sun <suntong...@gmail.com> wrote:
>>
>> All SQL DB statements need a sql.DB connection:
>>
>> var conn *sql.DB = ...
>> defer conn.Close()
>>
>> statement, err := conn.Prepare(SQL)
>>
>>
>> My question is, if I want to reuse the `conn` variable later on in the same
>> function,
>>
>> conn, err = sql.Open("mssql", NewConnString)
>
>If you didn't close conn here, then it will leak. The defer will close
>the second connection, not the first.
>You can add a second defer after opening the second connection. Or,
>use a different variable and defer closing of that as well.
>
>Closing the first connection manually before opening the second won't
>work. The first defer will try to close the first connection. Defer
>evaluates its arguments when it is declared, not when it runs.
>
>
>>
>>
>> Do I need to put another `defer conn.Close()` after it, or the first `defer
>> conn.Close()` still applies? Or I should call `conn.Close()` explicitly
>> beforehand?
>>
>> thanks
>>
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>
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I don't think that is true. The first defer will be scheduled with the first
conn arg (since it is evaluated at call time). You need another defer after the
second open. You will end up with Close being called twice from defer which is
what you want.
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