code: func serviceOAuth(certFilePath string) (*serviceOAuthAuthentication, error) {
  	// First we read the cert
  	certs := x509.NewCertPool()
  	pemData, err := ioutil.ReadFile(certFilePath)
  	if err != nil {
  		return nil, err
  	}
  	certs.AppendCertsFromPEM(pemData)
  	mTLSConfig := &tls.Config{
  		RootCAs: certs, //Add the cert as a TLS config
  	}
  	a := serviceOAuthAuthentication{
  		BaseUrl: "https://coinbase.com/",
  		Client: http.Client{
  			Transport: &http.Transport{
  				Dial:            dialTimeout,
  				TLSClientConfig: mTLSConfig,
  			},
  		},
  	}
  	return &a, nil
  }
docs: // ServiceOAuth instantiates ServiceOAuthAuthentication with the coinbase certificate file