httpc request twice,the second time return err of closed

`
-- 引入必要的Lua库
local http = require("resty.http")

-- 创建全局的连接池
local httpc_pool = {}
-- 获取参数变量url
local url = ngx.var.arg_url

if not url then
ngx.status = ngx.HTTP_BAD_REQUEST
ngx.say("Missing 'url' parameter")
ngx.exit(ngx.HTTP_BAD_REQUEST)
end

-- 从连接池中获取连接
local httpc = httpc_pool[url]
if not httpc then
-- 连接池中没有可用的连接，创建一个新的连接
httpc = http.new()
httpc_pool[url] = httpc
end

-- 发起HTTP请求获取URL的响应
local res, err = httpc:request_uri(url, {
method = "GET",
ssl_verify = false,
headers = {
["User-Agent"] = "Mozilla/5.0 (compatible; Lua-resty-http/0.15; +https://github.com/pintsized/lua-resty-http)",
}
})

if not res then
ngx.status = ngx.HTTP_INTERNAL_SERVER_ERROR
ngx.say("Failed to request meiya image URL: ", err)
ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
end

-- 获取响应的文本内容
local body = res.body

-- 请求并返回图片数据
res, err = httpc:request_uri("body ", {
method = "GET",
ssl_verify = false,
headers = {
["User-Agent"] = "Mozilla/5.0 (compatible; Lua-resty-http/0.15; +https://github.com/pintsized/lua-resty-http)",
}
})

if not res then
ngx.log(ngx.ERR, "request err.", err)
ngx.status = ngx.HTTP_INTERNAL_SERVER_ERROR
ngx.say('请求失败！',err)
ngx.exit(ngx.HTTP_INTERNAL_SERVER_ERROR)
end

ngx.header["Content-Type"] = res.headers["Content-Type"]
ngx.print(res.body)
ngx.flush(true)
`

this is my lua script; when i modify body as url constant, the second reuqest is all right. when body is a variable, second request's res is nil and err msg is closed.

can anyone figure out code's mistake?

Start with the posted Lua script and compare the two httpc:request_uri calls, including the URL value passed to the second call. Verify the intended response-derived URL and confirm that the second request completes without the closed error.