step1、install Xcode

step2、install xcpkg

step3、update xcpkg-formula-repository

xcpkg update

step4、build and install async

xcpkg install async  

xcpkg formula view async  

{{ formula }}

if the formula of async  dosn't meet your needs, you can edit it ⤵︎

xcpkg formula edit async  

after editing, you may want to rebuild this package ⤵︎

xcpkg install async