QMK micro to shift letters by double tap

DoubleTapAutoShift.c

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
  uint8_t basic_keycode = 0;
  if (keycode >= QK_LAYER_TAP && keycode <= QK_LAYER_TAP_MAX){
      basic_keycode = (uint8_t)(keycode & 0xFF);
  }
  
  switch(keycode) {
    case LT(0,KC_A):
      if (record->event.pressed) {
        if (record->tap.count == 2) {
          register_mods(MOD_BIT(KC_LSFT));
        }
        register_code(keycode);
      } else {
        unregister_code(keycode);
        if (record->tap.count == 2) {
          unregister_mods(MOD_BIT(KC_LSFT));
        }
      }
      return false;
      break;
  }
  return true;
}