@Override public final String getHeaderFieldKey(int position) {
    try {
      return getHeaders().name(position);
    } catch (IOException e) {
      return null;
    }
  }
Returns the value of the field corresponding to the {@code fieldName}, or
null if there is no such field. If the field has multiple values, the
last value is returned.
gateway/platforms/servlet/src/main/java/io/apiman/gateway/platforms/servlet/connectors/ok/HttpURLConnectionImpl.java