#include <ArduinoJson.h>

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32!");
}

void loop() {
  String json = "{\"sensor\":\"gps\",\"time\":1351824120}";

  JsonDocument doc;
  deserializeJson(doc, json);

  const char* sensor = doc["sensor"];
  long time          = doc["time"];

  Serial.println(time);
}