terraform：术语“ terraform”未被识别为cmdlet，函数，脚本文件或可运行程序的名称

Question

terraform : The term 'terraform' is not recognized as the name of a cmdlet,
function, script file, or operable program. Check the spelling of the name,
or if a path was included, verify that the path is correct and try again.
At line:1 char:1
+ terraform -help
+ ~~~~~~~~~
    + CategoryInfo          : ObjectNotFound: (terraform:String) [], CommandNotFoundException
    + FullyQualifiedErrorId : CommandNotFoundException