(Go) Get a Google People API OAuth2 Access Token

Demonstrates how to get a Google People OAuth2 access token from a desktop application or script.

For more information, see https://developers.google.com/people/v1/how-tos/authorizing

Chilkat Go Downloads Go Package for Windows, MacOS, Linux, Alpine Linux, Solaris

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    oauth2 := chilkat.NewOAuth2()
    var success bool

    // For Google OAuth2, set the ListenPort equal to the port specified in the authorized callback URI for the ClientID.
    // See http://cknotes.com/setup-google-account-for-google-drive-api-walkthrough/
    oauth2.SetListenPort(3017)

    oauth2.SetAuthorizationEndpoint("https://accounts.google.com/o/oauth2/v2/auth")
    oauth2.SetTokenEndpoint("https://www.googleapis.com/oauth2/v4/token")

    // Replace these with actual values.
    oauth2.SetClientId("GOOGLE-CLIENT-ID")
    oauth2.SetClientSecret("GOOGLE-CLIENT-SECRET")

    oauth2.SetCodeChallenge(true)
    oauth2.SetCodeChallengeMethod("S256")

    // See Google People API Scopes for more scopes.
    oauth2.SetScope("profile https://www.googleapis.com/auth/contacts https://www.googleapis.com/auth/contacts.other.readonly https://www.googleapis.com/auth/directory.readonly")

    // Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
    url := oauth2.StartAuth()
    if oauth2.LastMethodSuccess() != true {
        fmt.Println(oauth2.LastErrorText())
        oauth2.DisposeOAuth2()
        return
    }

    // At this point, your application should load the URL in a browser.
    // For example, 
    // in C#: System.Diagnostics.Process.Start(url);
    // in Java: Desktop.getDesktop().browse(new URI(url));
    // in VBScript: Set wsh=WScript.CreateObject("WScript.Shell")
    //              wsh.Run url
    // in Xojo: ShowURL(url)  (see http://docs.xojo.com/index.php/ShowURL)
    // in Dataflex: Runprogram Background "c:\Program Files\Internet Explorer\iexplore.exe" sUrl        
    // The Google account owner would interactively accept or deny the authorization request.

    // Add the code to load the url in a web browser here...
    // Add the code to load the url in a web browser here...
    // Add the code to load the url in a web browser here...
    // System.Diagnostics.Process.Start(url);

    // Now wait for the authorization.
    // We'll wait for a max of 30 seconds.
    numMsWaited := 0
    for (numMsWaited < 30000) && (oauth2.AuthFlowState() < 3) {
        oauth2.SleepMs(100)
        numMsWaited = numMsWaited + 100
    }

    // If there was no response from the browser within 30 seconds, then 
    // the AuthFlowState will be equal to 1 or 2.
    // 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
    // 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
    // In that case, cancel the background task started in the call to StartAuth.
    if oauth2.AuthFlowState() < 3 {
        oauth2.Cancel()
        fmt.Println("No response from the browser!")
        oauth2.DisposeOAuth2()
        return
    }

    // Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
    // The possible AuthFlowState values are:
    // 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
    // 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
    // 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
    if oauth2.AuthFlowState() == 5 {
        fmt.Println("OAuth2 failed to complete.")
        fmt.Println(oauth2.FailureInfo())
        oauth2.DisposeOAuth2()
        return
    }

    if oauth2.AuthFlowState() == 4 {
        fmt.Println("OAuth2 authorization was denied.")
        fmt.Println(oauth2.AccessTokenResponse())
        oauth2.DisposeOAuth2()
        return
    }

    if oauth2.AuthFlowState() != 3 {
        fmt.Println("Unexpected AuthFlowState:", oauth2.AuthFlowState())
        oauth2.DisposeOAuth2()
        return
    }

    // Save the full JSON access token response to a file.
    sbJson := chilkat.NewStringBuilder()
    sbJson.Append(oauth2.AccessTokenResponse())
    sbJson.WriteFile("qa_data/tokens/googlePeople.json","utf-8",false)

    // The saved JSON response looks like this:

    // {
    //   "access_token": "ya29.a0AfH6S ... LAZYFUkf0",
    //   "expires_in": 3599,
    //   "refresh_token": "1//0fL_Ov ... ee0",
    //   "scope": "https://www.googleapis.com/auth/contacts",
    //   "token_type": "Bearer"
    // }

    fmt.Println("OAuth2 authorization granted!")
    fmt.Println("Access Token = ", oauth2.AccessToken())

    oauth2.DisposeOAuth2()
    sbJson.DisposeStringBuilder()