"send_text" got no error meesage after browser closed

my lua code is just like this:

local file = io.popen("tail -f /var/log/ping.log")
for line in file:lines() do
local bytes, err = wb:send_text(line)
ngx.log(ngx.INFO, "LINE SENDED:",line,":",bytes,":",err)

if not bytes then
     ngx.log(ngx.ERR, "failed to send a text frame: ", err)
    return ngx.exit(444)
end

end
file:close()

after my browser(chrome/edge) closed，the "send_text" still return bytes and no error，which I hope a zero bytes and error msage like "the client connection is closed"

need help

Start at the send_text call in the provided Lua reproduction and trace how it handles a browser closing during the tail -f loop. Reproduce the Chrome or Edge disconnect, then verify that send_text reports zero bytes and an error such as a closed client connection instead of reporting success.