gistfile1.txt

int main(){
  ...
  std::thread videoProcTH([&]{
    EventBase evb;
    ClassA *aclass = new ClassA(&evb);
    evb.loopForever();
  });
}

class classA{
...
classA::requestData(fbstring url, std::function<void(fbstring)> callback){
  evb->runInEventBaseThread([=]() {
        CurlClient *curlClient = new CurlClient(evb, fbcurl, callback);
        HTTPConnector *connector_ = new HTTPConnector(curlClient, timer_.get());
        static const AsyncSocket::OptionMap opts{{{SOL_SOCKET, SO_REUSEADDR}, 1}};
        if (url.isSecure()) {
          connector_->connectSSL(
            evb, *addr, sslContext_, nullptr,
            std::chrono::milliseconds(12000), opts,
            folly::AsyncSocket::anyAddress(), curlClient->getServerName());
        } else {
          connector_->connect(evb, *addr, std::chrono::milliseconds(12000), opts);
        }
    });
 }
 ...
 }

Actually, there was another thread leading to the requestData which is why runInBaseThread was required.