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# Adding custom code

> Learn how to add custom logic and methods to your Go SDK with Fern. Extend generated clients with helper functions and custom code.

#### Enterprise feature

This feature is available only for the [Enterprise plan](https://buildwithfern.com/pricing). To get started, reach out to [support@buildwithfern.com](mailto:support@buildwithfern.com).

This page covers how to add custom logic and methods to your Go SDK.

## Adding custom logic

To get started adding custom code:

These steps cover adding a new custom file to the SDK. To preserve line-level edits to a generated file, use [Replay](/learn/sdks/overview/custom-code#replay) instead.

### Create a new file and add your custom logic

**`helper.go`**

```go title="helper.go"
func MyHelper() {
  fmt.Println("Hello World!")
}
```

### Add your file to `.fernignore`

**`.fernignore`**

```yaml {3} title=".fernignore"
# Specify files that shouldn't be modified by Fern

helper.go
```

### Consume the helper

Now your users can consume the helper function by importing it from the SDK.

```go
import "github.com/package/example"

example.MyHelper();
```

## Adding custom SDK methods

Fern also allows you to add custom methods to the SDK itself (e.g.
`client.my_method()` ) by inheriting the Fern generated client and then
extending it.

### Update `generators.yml` configuration

Name your Fern-generated client something like `BaseClient` to reflect that this client will be extended.

**`generators.yml`**

```yml {4} title="generators.yml"
- name: fern-go-sdk
    version: "..."
    config:
      clientName: BaseClient
```

### Import and extend the generated client

First, import the Fern generated base client and extend it. Then, add whatever methods you want.

**`client/my_client.go`**

```go title="client/my_client.go"
type MyClient struct {
  *Client // Embed the Fern generated client.
}

func NewMyClient(opts ...option.RequestOption) *MyClient {
  return &MyClient{
    Client: NewClient(opts...),
  }
}

func (m *MyClient) MyHelper() {
  fmt.Println("Hello World!")
}
```

### Update `.fernignore`

Add the `client/my_client.go.` to `.fernignore`.

**`.fernignore`**

```diff title=".fernignore"
+ client/my_client.go
```

### Consume the method

Instead of constructing the generated client, your users will want to construct the extended client.

**`main.go`**

```go title="main.go"
import exampleclient "github.com/package/example/client"

client := exampleclient.NewMyClient():
```

Now your users can consume the helper function by importing it from the SDK.

```go
client.MyHelper()
```

> Learn how to add custom logic and methods to your Go SDK with Fern. Extend generated clients with helper functions and custom code.