Close() on *net.UDPConn is not calling close syscall

addrinuse.go

package main

import "net"

const maxRecvSize = 0x2000

func main() {
	for i := 0; i < 100000; i++ {
		p, err := net.ListenPacket("udp", "127.0.0.1:3000")
		if err != nil {
			// Eventually: listen udp 127.0.0.1:3000: bind: address already in use
			panic(err)
		}
		go func() {
			var b [maxRecvSize]byte
			for {
				_, _, err := p.ReadFrom(b[:])
				if err != nil {
					return
				}
			}
		}()
		err = p.Close()
		if err != nil {
			panic(err)
		}
	}
}