code: func IsPublicIP(ip net.IP) bool {
  	if !ip.IsGlobalUnicast() {
  		return false
  	}
  
  	for _, mask := range privateMasks {
  		if mask.Contains(ip) {
  			return false
  		}
  	}
  
  	return true
  }
docs: // IsPublicIP returns true if the given IP can be routed on the Internet