在網路上搜尋很久都很少看到 Terraform module 正確使用 remote private registry 的方式，所以來分享一下。
Due to less information on the internet when I am searching how terraform module access remote private registry, so I decide to share this.

先講講 Terraform module 是如何運作。其實就是直接 clone 一份下來，所以等於你去 git clone。
First, we need to know how Terraform module work, that is git clone, Terraform will clone the module repo which you use.

而我們都知道，git分為 HTTP(S) 以及 SSH 兩種clone方式，所以在這邊兩種方式都會介紹 (居然連stackoverflow都找不到到資料 T_T)
And we know that you can clone a git repo by HTTP(S) and SSH, so I will also introduce both of these two ways.

For HTTP(S) Protocol:

module "base" {
    source = "git::https://bitbucket.org/davidh83110/terraform_modules.git/ec2"
}

For SSH Protocol:

module "base" {
    source = "git::ssh://[email protected]/davidh83110/terraform_modules.git//ec2"
}

在 SSH clone 方式裡，請使用 // 雙斜線來表示目錄 (i.e. //ec2)
Please use a double slash (//) to clone a directory (i.e. //ec2).

That’s all.