code: func NewNetAddress(addr net.Addr) *NetAddress {
  	tcpAddr, ok := addr.(*net.TCPAddr)
  	if !ok {
  		if flag.Lookup("test.v") == nil { // normal run
  			cmn.PanicSanity(cmn.Fmt("Only TCPAddrs are supported. Got: %v", addr))
  		} else { // in testing
  			return NewNetAddressIPPort(net.IP("0.0.0.0"), 0)
  		}
  	}
  	ip := tcpAddr.IP
  	port := uint16(tcpAddr.Port)
  	return NewNetAddressIPPort(ip, port)
  }
docs: // NewNetAddress returns a new NetAddress using the provided TCP
  // address. When testing, other net.Addr (except TCP) will result in
  // using 0.0.0.0:0. When normal run, other net.Addr (except TCP) will
  // panic.
  // TODO: socks proxies?