与'operator='不匹配(操作数类型'String'且"void")

我正在查询一个使用NodeMCU ESP8266微控制器返回JSON字符串的网页。来自网页的响应如下所示：

{"1":true,"2":false,"3":false,"4":true,"5":true,"6":false,"7":false,"8":false}

我使用的代码如下所示：

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <ArduinoJson.h>
String payload = "";
const char* ssid = "ssid";
const char* password = "password";
String url = "example.com/data.json";
void setup() {
Serial.begin(115200);
delay(2000); while (!Serial);
WiFi.begin(ssid, password);
while (WiFi.status() !=WL_CONNECTED){
delay(500);
Serial.print(".");
}
Serial.println(WiFi.localIP());
pinMode(D0, OUTPUT);
}
void loop() {
StaticJsonBuffer<100> jsonBuffer;
delay(5000);
HTTPClient http;
http.begin(url);
int httpCode = http.GET();
Serial.println(httpCode);
Serial.println(http.getString());
if (httpCode > 0) {
payload = http.getString();
}
http.end();
JsonObject& root = jsonBuffer.parseObject(payload);
Serial.println(payload);
if(!root.success()) {
Serial.println("parseObject() failed");
}
if(root["1"] == true) {
Serial.println("true");
}
digitalWrite(D0, !digitalRead(D0));
}

我相信它无法解析的原因是有效载荷变量以尾随换行符结尾。然后我尝试payload = payload.trim();但后来我得到了no match for 'operator=' (operand types are 'String' and 'void')所以我尝试了同样的问题payload = payload.replace("n,"");然后我再次尝试payload = String(payload);失败。我做错了什么？