### Install Google APIs Client Libraries

Source: https://github.com/googleapis/google-api-go-client/blob/main/README.md

Use 'go get' to install specific API client libraries for your Go project. This example shows how to get the tasks, moderator, and urlshortener v1 libraries.

```shell
$ go get google.golang.org/api/tasks/v1
$ go get google.golang.org/api/moderator/v1
$ go get google.golang.org/api/urlshortener/v1
```

--------------------------------

### Install Google API Client Library for Go

Source: https://github.com/googleapis/google-api-go-client/blob/main/GettingStarted.md

Use 'go get' to install a specific version of a Google API client library. This command fetches and installs the library, making it available for use in your Go projects.

```bash
$ go get -u google.golang.org/api/urlshortener/v1
```

--------------------------------

### Install URL Shortener API v1

Source: https://github.com/googleapis/google-api-go-client/wiki/GettingStarted

Use 'go get' to install a specific version of a Google API library. This command fetches and installs the urlshortener v1 API.

```bash
$ go get code.google.com/p/google-api-go-client/urlshortener/v1
```

--------------------------------

### Impersonate Credentials Example

Source: https://github.com/googleapis/google-api-go-client/blob/main/CHANGES.md

Demonstrates how to use the new impersonate package for credentials. This is the recommended approach for impersonation, replacing the experimental option.ImpersonateCredentials.

```go
import (
	"golang.org/x/oauth2/google"
	"golang.org/x/oauth2/impersonate"
)

func main() {
	// Use the new impersonate package for credentials.
	// See https://pkg.go.dev/google.golang.org/api/impersonate#example-CredentialsTokenSource-ServiceAccount
	client, err := impersonate.CredentialsTokenSource(ctx, impersonate.ServiceAccountOptions{
		TargetPrincipal: "my-service-account@my-project.iam.gserviceaccount.com",
		Scopes:          []string{cloudresourcemanager.CloudPlatformScope},
	})
	if err != nil {
		// handle error
	}

	// Use the client to create an authenticated HTTP client.
	authenticatedClient := google.NewClient(ctx, client)

	// Use the authenticated client to make API requests.
	// For example, to list projects:
	// projectsClient, err := resourcemanager.NewProjectsService(authenticatedClient)
	// ...
}
```

--------------------------------

### Generate Client from Local Discovery Document

Source: https://github.com/googleapis/google-api-go-client/blob/main/google-api-go-generator/README.md

Builds the generator and then uses a local discovery document to generate a Go client. The --cache=true flag enables caching of discovery documents, and --install ensures generated packages are installed.

```bash
go build -o google-api-go-generator && ./google-api-go-generator -cache=true -install -api_json_file=/path/to/file
```

--------------------------------

### Clone the google-api-go-client Repository

Source: https://github.com/googleapis/google-api-go-client/blob/main/CONTRIBUTING.md

Use this command to clone the repository to your local machine. Ensure you have Git installed.

```bash
git clone https://github.com/googleapis/google-api-go-client
```

--------------------------------

### Import URL Shortener API v1

Source: https://github.com/googleapis/google-api-go-client/wiki/GettingStarted

Import the installed Google API library into your Go program. The package name is typically the API name without the version.

```go
package main

import (
    "code.google.com/p/google-api-go-client/urlshortener/v1"
)
```

--------------------------------

### Call URL Shortener Get Method

Source: https://github.com/googleapis/google-api-go-client/wiki/GettingStarted

Make a call to the 'Get' method of the 'Url' sub-service in the urlshortener API. This retrieves information about a shortened URL.

```go
url, err := svc.Url.Get(shortURL).Do()
if err != nil {
    ...
}
fmt.Printf("The URL %s goes to %s\n", shortURL, url.LongUrl)
```

--------------------------------

### Conventional Commit Message Example

Source: https://github.com/googleapis/google-api-go-client/blob/main/CONTRIBUTING.md

Commit messages should follow the Conventional Commit specification. This example shows a commit message for adding a feature.

```git
functions: add gophers codelab
```

--------------------------------

### Instantiate API Service

Source: https://github.com/googleapis/google-api-go-client/wiki/GettingStarted

Create an API service instance by calling the 'New' function provided by the API library. This function requires an http.Client.

```go
svc, err := urlshortener.New(httpClient)
```

--------------------------------

### Import Google API Client Library in Go

Source: https://github.com/googleapis/google-api-go-client/blob/main/GettingStarted.md

Import necessary packages for interacting with Google APIs, including context, OAuth2, and the specific API client library. Ensure all required packages are listed for proper functionality.

```go
package main

import (
    "context"
    "golang.org/x/oauth2"
    "golang.org/x/oauth2/google"
    "google.golang.org/api/urlshortener/v1"
)
```

--------------------------------

### Tagging the Repository for Release

Source: https://github.com/googleapis/google-api-go-client/blob/main/RELEASING.md

Use this command to tag the repository with the next version during the release process. Ensure no other CLs are submitted before this step.

```bash
git tag $NV
```

--------------------------------

### Implement Wrapper for translate.Service

Source: https://github.com/googleapis/google-api-go-client/blob/main/testing.md

Implement the TranslateService interface by wrapping a concrete `translate.Service`. This wrapper handles the creation of the service and the translation request, abstracting the details of the Google API client's builder pattern.

```go
import (
    "context"
    "fmt"
    "log"
    "os"

    "google.golang.org/api/option"
    "google.golang.org/api/translate/v3"
)

type translateService struct {
    svc *translate.Service
}

// NewTranslateService creates a TranslateService.
func NewTranslateService(ctx context.Context, opts ...option.ClientOption) TranslateService {
    svc, err := translate.NewService(ctx, opts...)
    if err != nil {
        log.Fatalf("unable to create translate service, shutting down: %v", err)
    }
    return &translateService{svc}
}

func (t *translateService) TranslateText(text, language string) (string, error) {
    parent := fmt.Sprintf("projects/%s/locations/global", os.Getenv("GOOGLE_CLOUD_PROJECT"))
    resp, err := t.svc.Projects.Locations.TranslateText(parent, &translate.TranslateTextRequest{
        TargetLanguageCode: language,
        Contents:           []string{text},
    }).Do()
    if err != nil {
        return "", fmt.Errorf("unable to translate text: %v", err)
    }
    return resp.Translations[0].TranslatedText, nil
}
```

--------------------------------

### Initialize Sheets Service with Service Account Key File

Source: https://github.com/googleapis/google-api-go-client/blob/main/README.md

Authorize the Sheets API service client using a service account JSON key file. Use option.WithAuthCredentialsFile and specify the credential type and file path.

```go
client, err := sheets.NewService(ctx, option.WithAuthCredentialsFile(option.ServiceAccount, "path/to/keyfile.json"))
```

--------------------------------

### Configure 3-legged OAuth in Go

Source: https://github.com/googleapis/google-api-go-client/blob/main/GettingStarted.md

Set up an oauth2.Config for 3-legged OAuth flows. This requires your application's ClientID and ClientSecret, obtained from the Google Cloud Console, and the desired API scopes.

```go
var config = &oauth2.Config{
    ClientID:     "", // from https://console.developers.google.com/project/<your-project-id>/apiui/credential
    ClientSecret: "", // from https://console.developers.google.com/project/<your-project-id>/apiui/credential
    Endpoint:     google.Endpoint,
    Scopes:       []string{urlshortener.UrlshortenerScope},
}
```

--------------------------------

### Initialize URL Shortener Service

Source: https://github.com/googleapis/google-api-go-client/blob/main/README.md

Basic Go code to initialize the URL Shortener API service client using the default context. Ensure you handle the error returned by NewService.

```go
package main

import (
        "context"
        "net/http"

        "google.golang.org/api/urlshortener/v1"
)

func main() {
        ctx := context.Background()
        svc, err := urlshortener.NewService(ctx)
        // ...
}
```

--------------------------------

### Refresh Existing Client

Source: https://github.com/googleapis/google-api-go-client/blob/main/google-api-go-generator/README.md

Builds the generator and refreshes an existing client. It disables caching (--cache=false) to ensure the latest discovery document is fetched, specifies the API and version to refresh (--api=sevicename:vsomething), and sets the output directory (--gendir=..).

```bash
go build -o google-api-go-generator && ./google-api-go-generator -cache=false -install -api=sevicename:vsomething -gendir=..
```

--------------------------------

### Generating Go Client Code

Source: https://github.com/googleapis/google-api-go-client/blob/main/RELEASING.md

This command is used to generate or update the Go client code. It is typically run from the 'internal/version' directory.

```bash
go generate
```

--------------------------------

### Pushing the Release Tag

Source: https://github.com/googleapis/google-api-go-client/blob/main/RELEASING.md

After tagging the repository, push the tag to the origin to make the release public. This is a crucial step in the release workflow.

```bash
git push origin $NV
```

--------------------------------

### Initialize Sheets Service with Default Credentials

Source: https://github.com/googleapis/google-api-go-client/blob/main/README.md

Initialize the Google Sheets API service client using the default context and Application Default Credentials for authorization.

```go
// import "google.golang.org/api/sheets/v4"
client, err := sheets.NewService(ctx)
```

--------------------------------

### Add a Remote Fork

Source: https://github.com/googleapis/google-api-go-client/blob/main/CONTRIBUTING.md

After forking the repository, set up your fork as a remote named 'fork'. Replace GITHUB_USERNAME with your GitHub username.

```bash
git remote add fork git@github.com:GITHUB_USERNAME/google-api-go-client.git
```

--------------------------------

### Define Lightweight Mock for TranslateService

Source: https://github.com/googleapis/google-api-go-client/blob/main/testing.md

Define a lightweight mock implementation of the TranslateService interface for use in tests. This mock returns a predefined string and nil error, simplifying the testing of functions that depend on the TranslateService.

```go
import "testing"

// mockService fulfills the TranslateService interface.
type mockService struct{}

func (*mockService) TranslateText(text, language string) (string, error) {
    return "Hello World", nil
}
func TestTranslateTextHighLevel(t *testing.T) {
    svc := &mockService{}
    text, err := TranslateTextHighLevel(svc, "Hola Mundo", "en-US")
    if err != nil {
        t.Fatal(err)
    }
    if text != "Hello World" {
        t.Fatalf("got %q, want Hello World", text)
    }
}
```

--------------------------------

### Initialize Sheets Service with Token Source

Source: https://github.com/googleapis/google-api-go-client/blob/main/README.md

Authorize the Sheets API service client by providing an oauth2.TokenSource. This offers more control over the authorization process.

```go
tokenSource := ...
svc, err := sheets.NewService(ctx, option.WithTokenSource(tokenSource))
```

--------------------------------

### Running All Generation Tasks

Source: https://github.com/googleapis/google-api-go-client/blob/main/RELEASING.md

This command executes all necessary generation tasks for the clients. It is used by the nightly cron job for auto-regeneration.

```bash
make all
```

--------------------------------

### OAuth2 Configuration

Source: https://github.com/googleapis/google-api-go-client/wiki/GettingStarted

Define the OAuth2 configuration, including Client ID, Client Secret, scopes, and authentication URLs. Obtain Client ID and Secret from the Google API Console.

```go
var config = &oauth.Config{
    ClientId:     "", // from https://code.google.com/apis/console/
    ClientSecret: "", // from https://code.google.com/apis/console/
    Scope:        urlshortener.UrlshortenerScope,
    AuthURL:      "https://accounts.google.com/o/oauth2/auth",
    TokenURL:     "https://accounts.google.com/o/oauth2/token",
}
```

--------------------------------

### Test Translate Text Function with Fake HTTP Server

Source: https://github.com/googleapis/google-api-go-client/blob/main/testing.md

Tests the `TranslateText` function by creating a fake HTTP server using `httptest`. This fake server intercepts requests and returns predefined responses, allowing the test to run without making actual network calls. It uses `option.WithoutAuthentication()` and `option.WithEndpoint` to configure the service to use the test server.

```go
import (
    "context"
    "encoding/json"
    "net/http"
    "net/http/httptest"
    "testing"

    "google.golang.org/api/option"
    "google.golang.org/api/translate/v3"
)

func TestTranslateText(t *testing.T) {
    ctx := context.Background()
    ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        resp := &translate.TranslateTextResponse{
            Translations: []*translate.Translation{
                {TranslatedText: "Hello World"},
            },
        }
        b, err := json.Marshal(resp)
        if err != nil {
            http.Error(w, "unable to marshal request: "+err.Error(), http.StatusBadRequest)
            return
        }
        w.Write(b)
    }))
    defer ts.Close()
    svc, err := translate.NewService(ctx, option.WithoutAuthentication(), option.WithEndpoint(ts.URL))
    if err != nil {
        t.Fatalf("unable to create client: %v", err)
    }
    text, err := TranslateText(svc, "Hola Mundo", "en-US")
    if err != nil {
        t.Fatal(err)
    }
    if text != "Hello World" {
        t.Fatalf("got %q, want Hello World", text)
    }
}
```

--------------------------------

### Initialize Sheets Service with JSON Credentials

Source: https://github.com/googleapis/google-api-go-client/blob/main/README.md

Authorize the Sheets API service client directly using JSON credentials provided as a byte slice. Specify the credential type and the JSON key data.

```go
// where jsonKey is a []byte containing the JSON key
client, err := sheets.NewService(ctx, option.WithAuthCredentialsJSON(option.ServiceAccount, jsonKey))
```

--------------------------------

### Use API Key for Google API Authentication in Go

Source: https://github.com/googleapis/google-api-go-client/blob/main/GettingStarted.md

Authenticate Google API requests using an API key by creating an http.Client with a transport that includes the key. This is suitable for APIs that do not require user authorization.

```go
ctx := context.WithValue(context.Background(), oauth2.HTTPClient, &http.Client{
    Transport: &transport.APIKey{Key: developerKey},
})
oauthConfig := &oauth2.Config{ .... }
var token *oauth2.Token = .... // via cache, or oauthConfig.Exchange
httpClient := oauthConfig.Client(ctx, token)
svc, err := urlshortener.New(httpClient)
...
```

--------------------------------

### Create OAuth Transport Client

Source: https://github.com/googleapis/google-api-go-client/wiki/GettingStarted

Create an http.Client using an oauth.Transport. This client will automatically add OAuth2 authorization headers to requests.

```go
transport := &oauth.Transport{
    Token:     token,
    Config:    config,
    Transport: http.DefaultTransport,
}

httpClient := transport.Client()
```

--------------------------------

### API Key HTTP Client

Source: https://github.com/googleapis/google-api-go-client/wiki/GettingStarted

Create an http.Client that uses transport.APIKey to add an API key to requests. This is used for APIs that require API key authentication.

```go
client := &http.Client{
    Transport: &transport.APIKey{Key: developerKey},
}
```

--------------------------------

### Define High-Level TranslateService Interface

Source: https://github.com/googleapis/google-api-go-client/blob/main/testing.md

Define a high-level interface for the TranslateText method to abstract the underlying service's complexity. This interface is used by functions that need to translate text, allowing for easy substitution of real services with mocks during testing.

```go
// TranslateService is a facade of a `translate.Service`, specifically used to
// for translating text.
type TranslateService interface {
    TranslateText(text, language string) (string, error)
}

// TranslateTextHighLevel translates text to the given language using the
// provided service.
func TranslateTextHighLevel(service TranslateService, text, language string) (string, error) {
    return service.TranslateText(text, language)
}
```

--------------------------------

### Handle Google API Errors in Go

Source: https://github.com/googleapis/google-api-go-client/blob/main/GettingStarted.md

Check for specific Google API errors, such as 'Not Found' (http.StatusNotFound), by performing a type assertion on the returned error. This allows for granular error handling based on the API response.

```go
url, err := svc.Url.Get(shortURL).Do()
if err != nil {
    if e, ok := err.(*googleapi.Error); ok && e.Code == http.StatusNotFound {
        ...
    }
}
```

--------------------------------

### Translate Text Function

Source: https://github.com/googleapis/google-api-go-client/blob/main/testing.md

A function that translates text using the Google Translate API. It requires a `translate.Service` object, the text to translate, and the target language code. Ensure the `GOOGLE_CLOUD_PROJECT` environment variable is set.

```go
import (
    "fmt"
    "os"

    "google.golang.org/api/translate/v3"
)

// TranslateText translates text to the given language using the provided
// service.
func TranslateText(service *translate.Service, text, language string) (string, error) {
    parent := fmt.Sprintf("projects/%s/locations/global", os.Getenv("GOOGLE_CLOUD_PROJECT"))
    req := &translate.TranslateTextRequest{
        TargetLanguageCode: language,
        Contents:           []string{text},
    }
    resp, err := service.Projects.Locations.TranslateText(parent, req).Do()
    if err != nil {
        return "", fmt.Errorf("unable to translate text: %v", err)
    }
    return resp.Translations[0].TranslatedText, nil
}
```

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