我正在通过dockerfile使用node和nginx创建一个容器。它无缝发生。 但是，当我运行它时，出现以下错误。 我不知道这个。你能帮我吗？

2019/11/11 18:50:49 [emerg] 12#12: host not found in upstream "myproject-frontend:3000" in /etc/nginx/conf.d/default.conf:2
nginx: [emerg] host not found in upstream "myproject-frontend:3000" in /etc/nginx/conf.d/default.conf:2

nginx：在上游找不到[emerg]主机

# Stage 1
FROM node:latest as react-build
WORKDIR /app
COPY . ./
RUN yarn
RUN yarn build

# Stage 2 - the production environment
FROM andreilhicas/nginx-letsencrypt AS production
COPY ./nginx/nginx-tmp.conf /etc/nginx/conf.d/default.conf
COPY --from=react-build /app/build /usr/share/nginx/html
EXPOSE 3000
ENTRYPOINT ["./nginx-letsencrypt"]

upstream restgunicorn_server{
 server myproject-frontend:3000;
}

server {
  listen 80;
  server_name localhost;

  location /.well-known/acme-challenge/ {
    root /var/www/certbot;
  }
  location / {
        return 301 https://$host$request_uri;
  }
}
server {
    listen 443 ssl;
    server_name localhost;
    resolver 127.0.0.11 valid=30s;
     location / {
        proxy_pass http://restgunicorn_server;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_redirect off;
     }

    ssl_certificate /usr/share/nginx/certificates/fullchain.pem;
    ssl_certificate_key /usr/share/nginx/certificates/privkey.pem;
    include /etc/ssl-options/options-nginx-ssl.conf;
    ssl_dhparam /etc/ssl-options/ssl-dhparams.pem;
}