@Override
public String getAccessToken(String callBackUrl, String code) {
try {
GitHubApiUrlBuilder builder = createGitHubApiUrlBuilder(GitHubApiUrls.OAuthUrls.ACCESS_TOKEN_URL);
builder.withParameter(ParameterNames.CLIENT_ID, clientId);
builder.withParameter(ParameterNames.CLIENT_SECRET, secret);
builder.withParameter(ParameterNames.REDIRECT_URI, callBackUrl);
builder.withParameter(ParameterNames.CODE, code);
String response = convertStreamToString(callApiGet(builder.buildUrl()));
Matcher matcher = ApplicationConstants.ACCESS_TOKEN_PATTERN.matcher(response);