具体报错信息：ERROR: failed to solve: nginxinc/nginx-unprivileged:alpine: failed to resolve source metadata for docker.io/nginxinc/nginx-unprivileged:alpine: failed to authorize: failed to fetch oauth token: Post "https://auth.docker.io/token": read tcp 192.168.100.5:61091->34.226.69.105:443: wsarecv: An existing connection was forcibly closed by the remote host.
解决方式：确保能访问外网，先执行一次 docker pull nginxinc/nginx-unprivileged:alpine
然后再执行 docker build . -t 镜像名