attempt to index global 'wrk' (a nil value)

[SecretSun]

visual-wrk -d30s -c1024 -s ./post.lua http://127.0.0.1:8081/
./post.lua: ./post.lua:1: attempt to index global 'wrk' (a nil value)
PANIC: unprotected error in call to Lua API ([string "wrk"]:0: attempt to call field 'lookup' (a nil value))