在之前的版本这么配置没有问题，但在新的1.14上就有问题了(以let's encrypt为例)

server {
        listen 443 ssl;
        server_name  a.com;
        return 301 https://www.a.com$request_uri;
}


server {
        listen       443 ssl;
        server_name  www.a.com;

        ...
  
        ssl_certificate /etc/letsencrypt/live/a.com/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/a.com/privkey.pem;
}

一直不成功，改为下面：

server {
        listen 443 ssl;
        server_name  a.com;

        ssl_certificate /etc/letsencrypt/live/a.com/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/a.com/privkey.pem;
  
        return 301 https://www.a.com$request_uri;
}


server {
        listen       443 ssl;
        server_name  www.a.com;

        ...
  
        ssl_certificate /etc/letsencrypt/live/a.com/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/a.com/privkey.pem;
}