nginx泛域名rewrite

server {
    listen 80;
    server_name ~^(?<subdomain>\w+)\.example\.com$;

    location / {
        proxy_pass http://backend_server;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}

map $host $backend_server {
    default http://default_backend_server;
    "~^api\.(?<subdomain>\w+)\.example\.com$" http://api_backend_server;
    "~^www\.(?<subdomain>\w+)\.example\.com$" http://www_backend_server;
}

server {
    listen 80;
    server_name ~^(?<subdomain>\w+)\.example\.com$;

    location / {
        proxy_pass $backend_server;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }
}