socket.lua: attempt to concatenate local 'nserr' (a nil value)

[jurafa]

Hi.
I am sending you a stack trace of an error that happened to me while executing {'cat', '/proc/loadavg'} command. It has happened to me only once so far. I am using latest releases of lua-resty-exec and sock.exec.

2018/01/05 10:22:15 [error] 1871#0: *60665 send() failed (32: Broken pipe), client: *****, server: localhost, request: "POST /rpc HTTP/1.1", host: "*****", referrer: "http://localhost:4200/"
2018/01/05 10:22:15 [error] 1871#0: *60665 lua entry thread aborted: runtime error: /usr/local/openresty/site/lualib/resty/exec/socket.lua:38: attempt to concatenate local 'nserr' (a nil value)
stack traceback:
coroutine 0:
    /usr/local/openresty/site/lualib/resty/exec/socket.lua: in function 'ns_send'
    /usr/local/openresty/site/lualib/resty/exec/socket.lua:254: in function 'send_close'
    /usr/local/openresty/site/lualib/resty/exec.lua:115: in function 'prog'