race condition in dovecot plugin

[phemmer]

Bug report

telegraf/plugins/inputs/dovecot/dovecot.go

Lines 66 to 80 in c046232

	var outerr error
	if len(d.Filters) <= 0 {
	d.Filters = append(d.Filters, "")
	}
	for _, serv := range d.Servers {
	for _, filter := range d.Filters {
	wg.Add(1)
	go func(serv string, filter string) {
	defer wg.Done()
	outerr = d.gatherServer(serv, acc, d.Type, filter)
	}(serv, filter)
	}
	}

    var outerr error

    if len(d.Filters) <= 0 {
        d.Filters = append(d.Filters, "")
    }

    for _, serv := range d.Servers {
        for _, filter := range d.Filters {
            wg.Add(1)
            go func(serv string, filter string) {
                defer wg.Done()
                outerr = d.gatherServer(serv, acc, d.Type, filter)
            }(serv, filter)
        }
    }

outerr is not protected via a mutex.
Additionally, whichever call to d.gatherServer completes last wins writing to outerr. Meaning if one server fails, stores the error in outerr, but then the second server completes successfully, the first error is lost.