Cannot reconnect quickly when client close #142

Describe the bug
OS: Windows X86_64
When client close and quick reconnect(about Second * 1) to gnet server, gnet will not call OnOpened(c Conn). And net.Listener.Accept() return err "use of closed network connection"

To Reproduce
Steps to reproduce the behavior:

1. serve local tcp
2. use net.Dial to connect gnet server
3. close this connection when connected
4. wait 1 second
5. use net.Dial to connect gnet server
6. cannot connect to gnet server

Expected behavior
Expect to reconnect to server quickly

Screenshots
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System Info (please complete the following information):

• OS (e.g. Ubuntu 18.04): Windows 10
• Go version (e.g. Go 1.13): 1.15
• gnet version (e.g. v1.0.0): 1.3.0

Additional context
This issue is related to both udp server. When udp client try to reconnect quickly, it will not call React() method.