doc: use go get -d for installation (#2165)

Installing executables with 'go get' in module
mode is deprecated.

README.md

@@ -20,7 +20,7 @@ with large data-models.
 
 ## Quick Installation
 ```console
-go get entgo.io/ent/cmd/ent
+go get -d entgo.io/ent/cmd/ent
 ```
 
 For proper installation using [Go modules], visit [entgo.io website][entgo instal].

README_jp.md

@@ -19,7 +19,7 @@ src="https://s3.eu-central-1.amazonaws.com/entgo.io/assets/gopher_graph.png"/>
 
 ## クイックインストール
 ```console
-go get entgo.io/ent/cmd/ent
+go get -d entgo.io/ent/cmd/ent
 ```
 
 [Go modules]を使ったインストールについては、[entgo.io website][entgo instal]をご覧ください。

README_zh.md

@@ -17,7 +17,7 @@ ent是一个简单而又功能强大的Go语言实体框架，ent易于构建和
 
 ## 快速安装
 ```console
-go get entgo.io/ent/cmd/ent
+go get -d entgo.io/ent/cmd/ent
 ```
 
 请访问[entgo.io website][entgo instal]以使用[Go modules]进行正确安装。

doc/md/code-gen.md

@@ -9,7 +9,7 @@ The project comes with a codegen tool called `ent`. In order to install
 `ent` run the following command:
 
 ```bash
-go get entgo.io/ent/cmd/ent
+go get -d entgo.io/ent/cmd/ent
 ``` 
 
 ## Initialize A New Schema
@@ -60,7 +60,7 @@ go mod init <project>
 And then, re-run the following command in order to add `ent` to your `go.mod` file:
 
 ```console
-go get entgo.io/ent/cmd/ent
+go get -d entgo.io/ent/cmd/ent
 ```
 
 Add a `generate.go` file to your project under `<project>/ent`:

doc/md/getting-started.md

@@ -29,7 +29,7 @@ go mod init <project>
 ## Installation
 
 ```console
-go get entgo.io/ent/cmd/ent
+go get -d entgo.io/ent/cmd/ent
 ```
 
 After installing `ent` codegen tool, you should have it in your `PATH`.

doc/md/tutorial-setup.md

@@ -25,7 +25,7 @@ go mod init todo
 Run the following Go commands to install Ent, and tell it to initialize the project structure along with a `Todo` schema.
 
 ```console
-go get entgo.io/ent/cmd/ent
+go get -d entgo.io/ent/cmd/ent
 ```
 
 ```console