我究竟如何在Racket中使用线程宏？
遵循本指南：https://docs.racket-lang.org/threading/index.html我尝试(require threading)，但我收到此错误：
standard-module-name-resolver: collection not found
for module path: threading
collection: "threading"
in collection directories:
/Users/user/Library/Racket/6.9/collects
/Applications/Racket v6.9/collects
... [163 additional linked and package directories] in: threading
no packages suggestions are available .