(.NET Core C#) Get Google API Access Token using P12 Service Account Key

Demonstrates how to get a Google API access token using a P12 service account key.

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

// --------------------------------------------------------------------------------
// For a step-by-step guide for setting up your Google Workspace service account,
// see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
// --------------------------------------------------------------------------------

// First load the PKCS12 (.p12 / .pfx) into a PFX object.
Chilkat.Pfx pfx = new Chilkat.Pfx();
bool success = pfx.LoadPfxFile("qa_data/pfx/chilkat25-cbd7b42afbd8.p12","notasecret");
if (success != true) {
    Debug.WriteLine(pfx.LastErrorText);
    return;
}

Chilkat.AuthGoogle gAuth = new Chilkat.AuthGoogle();
success = gAuth.SetP12(pfx);

// The ISS is your service account email address ending in gserviceaccount.com.
string iss = "chilkatsvc@chilkat25.iam.gserviceaccount.com";

// The scope is always the following string:
string scope = "https://mail.google.com/";

// The sub is your company email address
string oauth_sub = "info@chilkat.xyz";

// The access token is valid for this number of seconds.
int numSec = 3600;

gAuth.EmailAddress = iss;
gAuth.Scope = scope;
gAuth.ExpireNumSeconds = numSec;
gAuth.SubEmailAddress = oauth_sub;

// Connect to www.googleapis.com
Chilkat.Socket tlsSock = new Chilkat.Socket();
success = tlsSock.Connect("www.googleapis.com",443,true,5000);
if (success != true) {
    Debug.WriteLine(tlsSock.LastErrorText);
    return;
}

// Send the request to obtain the access token.
success = gAuth.ObtainAccessToken(tlsSock);
if (success != true) {
    Debug.WriteLine(gAuth.LastErrorText);
    return;
}

// Examine the access token:
Debug.WriteLine("Access Token: " + gAuth.AccessToken);