Platformio:
<code>
lib_deps =
    esphome/ESPAsyncWebServer-esphome @ ^3.2.2
    alanswx/ESPAsyncWiFiManager @ ^0.31
</code>

<code>
#if defined(ESP8266)
#include <ESP8266WiFi.h>          
#else
#include <WiFi.h>
#endif
#include <ESPAsyncWebServer.h>
#include <ESPAsyncWiFiManager.h>         
#define WIFICONFIG_PIN D3

AsyncWebServer server(80);
DNSServer dns;
AsyncWiFiManager wifiManager(&server,&dns);


void initializewifimanager() {
    wifiManager.autoConnect("IoTWiFiConfig");
    pinMode(WIFICONFIG_PIN, INPUT);  // this line is for resetting, see next code for reset work
}
</code>    

Can put this code in startup() or in loop() to erase the SSID/Password
<code>
  if ( digitalRead(WIFICONFIG_PIN) == LOW ) {
     wifiManager.resetSettings();
     delay(3000);
     ESP.reset();
     delay(5000);
  }
</code>