Removing non ascii characters from request cookies for nginx

nginx-lua-remove-non-ascii-from-cookie.conf

server {
    set_by_lua_block $cookie_ascii {
        local cookie = ngx.var.http_cookie
        if cookie == nil or cookie == '' then return cookie end
        local cookie_ascii, n, err = ngx.re.gsub(cookie, "[^\\x00-\\x7F]", "")
        return cookie_ascii
    }

    listen 80;
    server_name example.com;
    
    location / {
        proxy_pass          http://localhost:5000;
        ...
        proxy_set_header    Cookie $cookie_ascii;
        ...
    }    
}