How to set up ssh proxy with Nginx (multiple domain)

nginx.conf

## Nginx Version > v1.9.2

stream {
  upstream ssh2 {
    server localhost:2204;
  }
  upstream ssh {
    server localhost:2203;
  }

  map $server_addr $map_ssh_domain {
    a.test.com ssh2;
    b.test.com ssh;
  }
  server {
    listen 443;
    proxy_pass    $map_ssh_domain;
  }
}