code: func createDefaultHTTPClient() *http.Client {
  	return &http.Client{
  		Transport: &http.Transport{
  			Proxy: http.ProxyFromEnvironment,
  			DialContext: (&net.Dialer{
  				Timeout:   30 * time.Second,
  				KeepAlive: 30 * time.Second,
  			}).DialContext,
  			TLSHandshakeTimeout:   15 * time.Second,
  			ResponseHeaderTimeout: 15 * time.Second,
  			ExpectContinueTimeout: 1 * time.Second,
  			TLSClientConfig: &tls.Config{
  				ServerName: os.Getenv(caServerNameEnvVar),
  				RootCAs:    initCertPool(),
  			},
  		},
  	}
  }
docs: // createDefaultHTTPClient Creates an HTTP client with a reasonable timeout value
  // and potentially a custom *x509.CertPool
  // based on the caCertificatesEnvVar environment variable (see the `initCertPool` function)