code: func Roundtrip(addr string) (string, error) {
  	conn, err := net.Dial("tcp", addr)
  	if err != nil {
  		return "", err
  	}
  	defer conn.Close()
  	return RoundtripWithConn(conn)
  }
docs: // Roundtrip is a single connection simplistic HTTP client
  // that allows us to bypass a connection pool to test load balancing
  // used in tests, as it only supports GET request on /