如何获取（IPv4）net.IPNet的广播地址？

Is there a built-in function to calculate the broadcast address of a net.IPNet struct?

The link @Dsafds has the answer. Here for history's sake, and so you don't have to read through the thread yourself. Code is Mikio Hara's with minor modifications made by me.

func lastAddr(n *net.IPNet) (net.IP, error) { // works when the n is a prefix, otherwise...
    if n.IP.To4() == nil {
        return net.IP{}, errors.New("does not support IPv6 addresses.")
    }
    ip := make(net.IP, len(n.IP.To4()))
    binary.BigEndian.PutUint32(ip, binary.BigEndian.Uint32(n.IP.To4())|^binary.BigEndian.Uint32(net.IP(n.Mask).To4()))
    return ip, nil
}