websocket部署时发生Handshake failed due to invalid Upgrade header的解决方案。

解决办法：在 Nginx ，location 中添加以下代码：

　proxy_set_header Upgrade $http_upgrade;
　proxy_set_header Connection  "upgrade";

server {
    listen 80;
    server_name localhost;
    location / {
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_set_header X-NginX-Proxy true;
 
        # prevents 502 bad gateway error
        proxy_buffers 8 32k;
        proxy_buffer_size 64k;
 
        proxy_pass http://127.0.0.1:8080;
        proxy_redirect off;
  
        # enables WS support
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection  "upgrade";
    }
}