ESP8266 WifiManager resetSettings via WebServer GET

Hi,

just have problems to reset the stored WifiManager Settings by accessing an URL (/resetWifi).
Unfortunately getting compile error:

AutoConnect-Webserver:60:5: error: 'wifiManager' is not captured
     wifiManager.resetSettings();
     ^
exit status 1
'wifiManager' is not captured

Here my Code:

#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <DNSServer.h>
#include <ESP8266mDNS.h>
#include <WiFiManager.h> 

MDNSResponder mdns;

ESP8266WebServer server(80);

String webPage = "";
int gpio2_pin = 2;

void setup(void){
  Serial.begin(115200);
  WiFiManager wifiManager;
  //wifiManager.resetSettings();
  wifiManager.autoConnect("AutoConnectAP");
  Serial.println("connected...yeey :)");
  
  webPage += "<h1>ESP8266 Web Server</h1>";
  webPage += "<p>LED <a href=\"socket2On\"><button>ON</button></a>&nbsp;<a href=\"socket2Off\"><button>OFF</button></a></p>";

  // preparing GPIOs
  pinMode(gpio2_pin, OUTPUT);
  digitalWrite(gpio2_pin, LOW);
  
  delay(1000);
  Serial.begin(115200);
  //WiFi.begin(ssid, password);
  Serial.println("");

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("");
  Serial.print("Connected to ");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
  
  if (mdns.begin("esp8266", WiFi.localIP())) {
    Serial.println("MDNS responder started");
  }
  
  server.on("/", [](){
    server.send(200, "text/html", webPage);
  });
  
  server.on("/resetWifi", [](){
    server.send(200, "text/html", "WIFI RESETED!");
    wifiManager.resetSettings();
    delay(1000);
  });
  
  server.on("/socket2On", [](){
    server.send(200, "text/html", webPage);
    digitalWrite(gpio2_pin, HIGH);
    delay(1000);
  });
  
  server.on("/socket2Off", [](){
    server.send(200, "text/html", webPage);
    digitalWrite(gpio2_pin, LOW);
    delay(1000); 
  });
  
  server.begin();
  Serial.println("HTTP server started");
}
 
void loop(void){
  server.handleClient();
}

Any idea?
-Thanks