private final OkHttpClient client;

  public CustomTrust() {
    // This implementation just embeds the PEM files in Java strings; most applications will
    // instead read this from a resource file that gets bundled with the application.

    HandshakeCertificates certificates = new HandshakeCertificates.Builder()
        .addTrustedCertificate(letsEncryptCertificateAuthority)

    Call call = httpClient.newCall(request);
    try (Response response = call.execute()) {
      JsonAdapter<OAuthSession> jsonAdapter = moshi.adapter(OAuthSession.class);
      return jsonAdapter.fromJson(response.body().source());
    }
  }

  /** See https://api.slack.com/methods/rtm.start. */
  public RtmStartResponse rtmStart(String accessToken) throws IOException {
    HttpUrl url = baseUrl.newBuilder("rtm.start")

        .setBody(fileToBytes(file))
        .addHeader("content-type: " + contentType(path));
  }

  private Buffer fileToBytes(File file) throws IOException {
    Buffer result = new Buffer();
    result.writeAll(Okio.source(file));
    return result;
  }

  private String contentType(String path) {
    if (path.endsWith(".png")) return "image/png";
    if (path.endsWith(".jpg")) return "image/jpeg";

    String login;
    int contributions;
  }

  public static void main(String... args) throws Exception {
    OkHttpClient client = new OkHttpClient();

    // Create request for remote resource.
    Request request = new Request.Builder()
        .url(ENDPOINT)
        .build();

    // Execute the request and retrieve the response.
    try (Response response = client.newCall(request).execute()) {

      // Consume and discard the response body.
      response.body().source().readByteString();
    }

    System.out.println("REQUEST 2 (pooled connection)");
    try (Response response = client.newCall(request).execute()) {
      // Consume and discard the response body.
      response.body().source().readByteString();
    }
  }

  public static void main(String... args) throws Exception {

    try (Response response = client.newCall(request).execute()) {
      if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

      Gist gist = gistJsonAdapter.fromJson(response.body().source());

      for (Map.Entry<String, GistFile> entry : gist.files.entrySet()) {
        System.out.println(entry.getKey());
        System.out.println(entry.getValue().content);
      }
    }
  }