Go Requires Chilkat v10.1.2+

Get GMail SMTP OAuth2 Access Token for Desktop App

See more OAuth2 Examples

This example show how to obtain a Gmail SMTP OAuth2 access token from a desktop application or script, enabling the use of XOAUTH2 authentication. Go

    success := false

    //  To further clarify, see OAuth 2.0 Authorization Flow

    oauth2 := chilkat.NewOAuth2()

    //  For Google OAuth2, set the listen port equal to the port used
    //  in the Authorized Redirect URL for the Client ID.
    //  For example, in this case the Authorized Redirect URL would be http://localhost:55568/
    //  Your app should choose a port not likely not used by any other application.
    oauth2.SetListenPort(55568)

    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")

    //  To use Gmail's OAuth2 for sending emails via the SMTP protocol, you need to request the https://mail.google.com/ scope. 
    //  See About GMail SMTP OAuth2 Scopes
    oauth2.SetScope("https://mail.google.com/")

    //  Begin the OAuth2 Authorization code 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
    }

    //  Launch the default browser on the system and navigate to the url.
    //  The LaunchBrowser method was added in Chilkat v10.1.2.
    success = oauth2.LaunchBrowser(*url)
    if success == false {
        fmt.Println(oauth2.LastErrorText())
        oauth2.DisposeOAuth2()
        return
    }

    //  Wait for the user to approve or deny authorization in the browser.
    numMsWaited := 0
    for (numMsWaited < 90000) && (oauth2.AuthFlowState() < 3) {
        oauth2.SleepMs(100)
        numMsWaited = numMsWaited + 100
    }

    //  If the browser does not respond within the specified time, AuthFlowState will be:
    //  
    //  1: Waiting for Redirect – The OAuth2 background thread is waiting for the browser's redirect request.
    //  2: Waiting for Final Response – The thread is awaiting the final access token response.
    //  In either case, cancel the background task initiated by StartAuth.

    if oauth2.AuthFlowState() < 3 {
        oauth2.Cancel()
        fmt.Println("No response from the browser!")
        oauth2.DisposeOAuth2()
        return
    }

    //  Check AuthFlowState to determine if authorization was granted, denied, or failed:
    //  
    //  3: Success – OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
    //  4: Access Denied – OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
    //  5: Failure – OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

    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/_gmailSmtp.json","utf-8",false)

    //  The saved JSON response looks like this:

    //  	{
    //  	 "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtBBBHkZzrwlARkwX6R3O0PCDEzRlfaQ",
    //  	 "token_type": "Bearer",
    //  	 "expires_in": 3600,
    //  	 "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
    //  	}
    //  
    fmt.Println("OAuth2 authorization granted!")
    fmt.Println("Access Token = ", oauth2.AccessToken())

    oauth2.DisposeOAuth2()
    sbJson.DisposeStringBuilder()