Fix size issue when deserialising on Windows (#144)

ping.go

@@ -472,8 +472,7 @@ func (p *Pinger) recvICMP(
 		case <-p.done:
 			return nil
 		default:
-			// ICMP messages have an 8-byte header.
+			bytes := make([]byte, p.getMessageLength())
-			bytes := make([]byte, p.Size+8)
 			if err := conn.SetReadDeadline(time.Now().Add(time.Millisecond * 100)); err != nil {
 				return err
 			}

utils_other.go

@@ -0,0 +1,8 @@
+// +build !windows
+
+package ping
+
+// Returns the length of an ICMP message.
+func (p *Pinger) getMessageLength() int {
+	return p.Size + 8
+}

utils_windows.go

@@ -0,0 +1,16 @@
+// +build windows
+
+package ping
+
+import (
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
+)
+
+// Returns the length of an ICMP message, plus the IP packet header.
+func (p *Pinger) getMessageLength() int {
+	if p.ipv4 {
+		return p.Size + 8 + ipv4.HeaderLen
+	}
+	return p.Size + 8 + ipv6.HeaderLen
+}