Build nginx gogs in docker, both in the same docker network.
Test conditions:

1. Gogs can be accessed via IP+ port
2. Nginx can be started and can proxy another html page and be accessed through a secondary domain name.

Question:
Gogs cannot be accessed through the secondary domain name. Error reporting:502 Bad Gateway nginx/1.15.6
The domain name in the code is replaced by # domain name

error.log

2018/11/15 06: 53: 21 [Error] 5 # 5: * 1 Connect () Failed (111: Connection Used) While Connecting to Upstream, Client: 14.153.77.141, Server: # Domain Name.  Request: "get/http/2.0", upstream: "http://172.18.0.3: 10080/",host: "# domain name"

nginx.config

user nginx;
 worker_processes auto;
 error_log /etc/nginx/err/error.log;
 
 events {
 worker_connections 1024;
 }
 
 http {
 sendfile            on;
 tcp_nopush          on;
 tcp_nodelay         on;
 keepalive_timeout   65;
 types_hash_max_size 2048;
 
 include             mime.types;
 default_type        application/octet-stream;
 include /etc/nginx/conf.d/*.conf;
 
 server {
 listen       80 default_server;
 listen       [::]:80 default_server;
 server_name  _;
 
 location / {
 }
 
 error_page 404 /404.html;
 location = /40x.html {
 }
 
 error_page 500 502 503 504 /50x.html;
 location = /50x.html {
 }
 }
 }

default.conf

server {
 listen 80;
 Server_name # normal domain name;
 return 301 https://$server_name$request_uri;
 }
 server{
 listen 443 ssl http2;
 Server_name # normal domain name;
 Ssl_certificate # normal key;
 Ssl_certificate_key # normal key;
 ssl_session_timeout 10m;
 ssl_ciphers ECDHE-RSA-AES128-GCM-SHA256:HIGH:!  aNULL:d!  MD5:!  RC4:!  DHE;
 ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
 location / {
 proxy_pass http://gogs:10080/;
 proxy_redirect default;
 }
 access_log  /etc/nginx/err/gogs.log;
 }

App.ini of gogs

[server]
 DOMAIN           = http://127.0.0.1
 HTTP_PORT        = 3000
 ROOT_URL         = http://127.0.0.1:10080/
 DISABLE_SSH      = false
 SSH_PORT         = 10022
 START_SSH_SERVER = true
 OFFLINE_MODE     = false
 ENABLE_GZIP         = true