`{   "builder": {     "gc": {       "defaultKeepStorage": "20GB",       "enabled": true,     }   },   "experimental": false,   "registry-mirrors": \[     "https://registry.docker-cn.com",     "https://inhuf6a9.mirror.aliyuncs.com",     "https://hub-mirror.c.163.com",     "https://docker.mirrors.ustc.edu.cn",     "https://reg-mirror.qiniu.com"   \] }`