Kisesy/gscan_quic: scan.go; 35 LoC

Found a possible issue in [Kisesy/gscan_quic](https://www.github.com/Kisesy/gscan_quic) at [scan.go](https://github.com/Kisesy/gscan_quic/blob/435ce8ea69836fdad3edd46b4d3b142016b0b79c/scan.go#L71-L105)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first issue it finds, so please do not limit your consideration to the contents of the below message.

> range-loop variable ip used in defer or goroutine at line 86

[Click here to see the code in its original context.](https://github.com/Kisesy/gscan_quic/blob/435ce8ea69836fdad3edd46b4d3b142016b0b79c/scan.go#L71-L105)

Click here to show the 35 line(s) of Go which triggered the analyzer.

```go
for ip := range ch {
srs.IncScanCounter()

if gcfg.VerifyPing {
start := time.Now()
if err := Ping(ip, gcfg.ScanMaxPingRTT); err != nil {
continue
}
if time.Since(start) < gcfg.ScanMinPingRTT {
continue
}
}

done := make(chan struct{}, 1)
go func() {
r := testip(ip, cfg)
if r != nil {
if srs.RecordSize() >= cfg.RecordLimit {
close(done)
return
}
srs.AddRecord(r)
}
done <- struct{}{}
}()

timer.Reset(cfg.ScanMaxRTT + 100*time.Millisecond)
select {
case <-ctx.Done():
return
case <-timer.C:
log.Println(ip, "timeout")
case <-done:
}
}

```

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commit ID: 435ce8ea69836fdad3edd46b4d3b142016b0b79c