user78117: Heres my code:
#include <WiFi.h>
#include <HTTPClient.h> 
#include <ArduinoJson.h>

const char* ssid = "wifiSSID";
const char* password =  "wifiPassword";

int sleepTime = 0;
HTTPClient http;

void setup() {
  Serial.begin(115200);

  Serial.println("START WIFI");
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
      delay(500);
      Serial.print(".");
  }

  http.begin("http://ip-address:3000/start?appid=1%2B6vIswDqSmXONCjq4rLtTMd9O2CHEQ4Oe");
  int httpCode = http.GET();
  String payload = http.getString();

  StaticJsonDocument<256> doc;
  deserializeJson(doc, payload);
  sleepTime = doc["sleep"];

  if (sleepTime > 0) {
    Serial.println("Sleeping for: " + sleepTime);
    delay(sleepTime);
    sleepTime = 0;
  }
}

void loop() {
  // Sensor stuff
}

Heres the error:
START WIFI
.........Guru Meditation Error: Core  1 panic'ed (Interrupt wdt timeout on CPU1)
Core 1 register dump:
PC      : 0x4000c271  PS      : 0x00060034  A0      : 0x8008a48c  A1      : 0x3ffb1c60  
A2      : 0x3ffb0058  A3      : 0x3f41ae58  A4      : 0x00000014  A5      : 0x3ffbfea0  
A6      : 0x3ffbfee8  A7      : 0x00000001  A8      : 0x00000001  A9      : 0x3f41ae59  
A10     : 0x000000a5  A11     : 0x30303030  A12     : 0x8008b043  A13     : 0x3ffbfe70  
A14     : 0x00000008  A15     : 0x00000001  SAR     : 0x00000012  EXCCAUSE: 0x00000006  
EXCVADDR: 0x00000000  LBEG    : 0x400014fd  LEND    : 0x4000150d  LCOUNT  : 0xfffffffa  

ELF file SHA256: 0000000000000000

Backtrace: 0x4000c271:0x3ffb1c60 0x4008a489:0x3ffb1c80 0x4008c034:0x3ffb1ca0 0x4008bfea:0x3ffb1cc0 0x400d5e5c:0x3f725c88

Core 0 register dump:
PC      : 0x40165582  PS      : 0x00060634  A0      : 0x8015196e  A1      : 0x3ffbc120  
A2      : 0x00000000  A3      : 0x00000001  A4      : 0x80084032  A5      : 0x3ffbf870  
A6      : 0x00060d20  A7      : 0x00000000  A8      : 0x801503f6  A9      : 0x3ffbc0f0  
A10     : 0x00000000  A11     : 0x00000001  A12     : 0x80084032  A13     : 0x3ffbf870  
A14     : 0x00000000  A15     : 0x3ffbc218  SAR     : 0x00000000  EXCCAUSE: 0x00000006  
EXCVADDR: 0x00000000  LBEG    : 0x00000000  LEND    : 0x00000000  LCOUNT  : 0x00000000  

ELF file SHA256: 0000000000000000

Backtrace: 0x40165582:0x3ffbc120 0x4015196b:0x3ffbc140 0x4008b031:0x3ffbc160 0x40089882:0x3ffbc180

Rebooting...
ets Jun  8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1216
ho 0 tail 12 room 4
load:0x40078000,len:10944
load:0x40080400,len:6388
entry 0x400806b4

What should I do?

user53909: I got this problem too with the latest IDF version..
check the IDF version as it seems the problem with RTOS handling both cores together.
The solution was for me to downgrade the IDF version to 3.0.0

78117: <p>Heres my code:</p>
<pre><code>#include &lt;WiFi.h&gt;
#include &lt;HTTPClient.h&gt; 
#include &lt;ArduinoJson.h&gt;

const char* ssid = &quot;wifiSSID&quot;;
const char* password =  &quot;wifiPassword&quot;;

int sleepTime = 0;
HTTPClient http;

void setup() {
  Serial.begin(115200);

  Serial.println(&quot;START WIFI&quot;);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
      delay(500);
      Serial.print(&quot;.&quot;);
  }

  http.begin(&quot;http://ip-address:3000/start?appid=1%2B6vIswDqSmXONCjq4rLtTMd9O2CHEQ4Oe&quot;);
  int httpCode = http.GET();
  String payload = http.getString();

  StaticJsonDocument&lt;256&gt; doc;
  deserializeJson(doc, payload);
  sleepTime = doc[&quot;sleep&quot;];

  if (sleepTime &gt; 0) {
    Serial.println(&quot;Sleeping for: &quot; + sleepTime);
    delay(sleepTime);
    sleepTime = 0;
  }
}

void loop() {
  // Sensor stuff
}
</code></pre>
<p>Heres the error:</p>
<pre><code>START WIFI
.........Guru Meditation Error: Core  1 panic'ed (Interrupt wdt timeout on CPU1)
Core 1 register dump:
PC      : 0x4000c271  PS      : 0x00060034  A0      : 0x8008a48c  A1      : 0x3ffb1c60  
A2      : 0x3ffb0058  A3      : 0x3f41ae58  A4      : 0x00000014  A5      : 0x3ffbfea0  
A6      : 0x3ffbfee8  A7      : 0x00000001  A8      : 0x00000001  A9      : 0x3f41ae59  
A10     : 0x000000a5  A11     : 0x30303030  A12     : 0x8008b043  A13     : 0x3ffbfe70  
A14     : 0x00000008  A15     : 0x00000001  SAR     : 0x00000012  EXCCAUSE: 0x00000006  
EXCVADDR: 0x00000000  LBEG    : 0x400014fd  LEND    : 0x4000150d  LCOUNT  : 0xfffffffa  

ELF file SHA256: 0000000000000000

Backtrace: 0x4000c271:0x3ffb1c60 0x4008a489:0x3ffb1c80 0x4008c034:0x3ffb1ca0 0x4008bfea:0x3ffb1cc0 0x400d5e5c:0x3f725c88

Core 0 register dump:
PC      : 0x40165582  PS      : 0x00060634  A0      : 0x8015196e  A1      : 0x3ffbc120  
A2      : 0x00000000  A3      : 0x00000001  A4      : 0x80084032  A5      : 0x3ffbf870  
A6      : 0x00060d20  A7      : 0x00000000  A8      : 0x801503f6  A9      : 0x3ffbc0f0  
A10     : 0x00000000  A11     : 0x00000001  A12     : 0x80084032  A13     : 0x3ffbf870  
A14     : 0x00000000  A15     : 0x3ffbc218  SAR     : 0x00000000  EXCCAUSE: 0x00000006  
EXCVADDR: 0x00000000  LBEG    : 0x00000000  LEND    : 0x00000000  LCOUNT  : 0x00000000  

ELF file SHA256: 0000000000000000

Backtrace: 0x40165582:0x3ffbc120 0x4015196b:0x3ffbc140 0x4008b031:0x3ffbc160 0x40089882:0x3ffbc180

Rebooting...
ets Jun  8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1216
ho 0 tail 12 room 4
load:0x40078000,len:10944
load:0x40080400,len:6388
entry 0x400806b4
</code></pre>
<p>What should I do?</p>
 53909: <p>I got this problem too with the latest IDF version..
check the IDF version as it seems the problem with RTOS handling both cores together.</p>
<p>The solution was for me to downgrade the IDF version to 3.0.0</p>
