Firebase stream 'connection lost' error when analogRead is used in loop - firebase

Question

I am using ESP8266 & Firebase to control my fan speed. I want to get analog input from a potentiometer and send data to firebase realtime database. But when I analogRead in loop, firebase stream gives error
"Set string...
FAILED
REASON: connection lost".
When analogRead is removed code works perfectly.
void loop()
{
sensorValue = analogRead(A0);
if (Firebase.ready() && (millis() - sendDataPrevMillis > 150000 || sendDataPrevMillis == 0))
{
sendDataPrevMillis = millis();
count++;
String Path = path + "/String";
String Value = "Hello World! " + String(count);
Serial.println("------------------------------------");
Serial.println("Set string...");
if (Firebase.setString(fbdo, Path.c_str(), Value.c_str()))
{
Serial.println("PASSED");
Serial.println("PATH: " + fbdo.dataPath());
Serial.println("TYPE: " + fbdo.dataType());
Serial.print("VALUE: ");
printResult(fbdo); //see addons/RTDBHelper.h
Serial.println("------------------------------------");
Serial.println();
}
else
{
Serial.println("FAILED");
Serial.println("REASON: " + fbdo.errorReason());
Serial.println("------------------------------------");
Serial.println();
}
}
if (Firebase.ready())
{
if (!Firebase.readStream(fbdo))
{
Serial.println("------------------------------------");
Serial.println("Can't read stream data...");
Serial.println("REASON: " + fbdo.errorReason());
Serial.println("------------------------------------");
Serial.println();
}
if (fbdo.streamTimeout())
{
Serial.println("Stream timeout, resume streaming...");
Serial.println();
}
if (fbdo.streamAvailable())
{
Serial.println("------------------------------------");
Serial.println("Stream Data available...");
Serial.println("STREAM PATH: " + fbdo.streamPath());
Serial.println("EVENT PATH: " + fbdo.dataPath());
Serial.println("DATA TYPE: " + fbdo.dataType());
Serial.println("EVENT TYPE: " + fbdo.eventType());
Serial.print("VALUE: ");
printResult(fbdo); //see addons/RTDBHelper.h
Serial.println("------------------------------------");
Serial.println();
}
}
}