code: func CanonicalAddr(url *url.URL) string {
  	addr := url.Host
  	if !hasPort(addr) {
  		return addr + ":" + portMap[url.Scheme]
  	}
  	return addr
  }
docs: // FROM: http://golang.org/src/net/http/transport.go
  // canonicalAddr returns url.Host but always with a ":port" suffix