Openresty 每隔固定时间 打印一个字符示例接口

用途：方便测试 Server-Sent Events（SSE）

server {
    listen 80 ; 
    server_name localhost; 
    index index.php index.html index.htm default.php default.htm default.html; 
    proxy_set_header Host $host; 
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; 
    proxy_set_header X-Forwarded-Host $server_name; 
    proxy_set_header X-Real-IP $remote_addr; 
    proxy_http_version 1.1; 
    proxy_set_header Upgrade $http_upgrade; 
    proxy_set_header Connection $http_connection; 
    access_log /www/sites/localhost/log/access.log main; 
    error_log /www/sites/localhost/log/error.log; 
    location ^~ /.well-known/acme-challenge {
        allow all; 
        root /usr/share/nginx/html; 
    }
    location /print_hello_world {
        #default_type text/event-stream;  
        default_type text/html;  
        proxy_buffering off;
        content_by_lua_block {
            local str = "Hello,World"
            local len = string.len(str)

            local result = ""
            for i = 1, len do
                result = result.. string.sub(str, i, i)
                ngx.say(string.sub(str, i, i))
                ngx.flush(true)  
               ngx.sleep(0.5)
            end
            ngx.say("-----".. result .."-----") 
            ngx.flush(true)
        }
    }
    root /www/sites/localhost/index; 
    error_page 404 /404.html; 
}