fixup! fix: avoid data race for PacketsSent

Signed-off-by: Per Hallgren <[email protected]>

ping.go

@@ -858,7 +858,9 @@ func (p *Pinger) processPacket(recv *packet) error {
 		inPkt.Seq = pkt.Seq
 		// If we've already received this sequence, ignore it.
 		if _, inflight := p.awaitingSequences[*pktUUID][pkt.Seq]; !inflight {
+			p.statsMu.Lock()
 			p.PacketsRecvDuplicates++
+			p.statsMu.Unlock()
 			if p.OnDuplicateRecv != nil {
 				p.OnDuplicateRecv(inPkt)
 			}