@Override public final String getHeaderField(int position) {
    try {
      return getHeaders().value(position);
    } catch (IOException e) {
      return null;
    }
  }
Returns the value of the field at {@code position}. Returns null if there
are fewer than {@code position} headers.
gateway/platforms/servlet/src/main/java/io/apiman/gateway/platforms/servlet/connectors/ok/HttpURLConnectionImpl.java