Multiple multicast listeners in different goroutines

[王富民awaw]

Hi Gophers and network experts,

I am calling `net.ListenMulticastUDP` in each http handler, attempting to act as a fan-out proxy to multiple browsers, since browsers cannot connect to UDP directly.

However, at any given time, only one single UDP listener is able to read data from the socket.

Only when the first browser disconnects, can the second browser start receiving subsequent data.

I wonder is this a limitation on `net.ListenMulticastUDP`, or is this a limitation of the UDP protocol itself?