Adwords api authentication with service account

[vyurbonas]

Actions taken
This is my App.config section :

<add key="OAuth2Mode" value="SERVICE_ACCOUNT" />
<add key="OAuth2PrnEmail" value="*****" />
<add key="OAuth2SecretsJsonPath" value="******.json" />
<add key="DeveloperToken" value="***********"/>
<add key = 'LoginCustomerId' value = '*********' />

Expected result
Authentication with service account without any interaction from the user

Actual result
Got error:"Missing required parameter: refresh_token", Uri:""

** Most likely cause of error (suggested by support via email) and workaround:
Looks like reading the OAuth2Mode from App.config in this method.
https://github.com/googleads/google-ads-dotnet/blob/master/src/Config/GoogleAdsConfig.cs#L487

As a workaround, if you set

var client = new GoogleAdsClient();
client.Config.OAuth2Mode = OAuth2Flow.SERVICE_ACCOUNT;

Should work.

[AnashOommen]

I thought this made it into v3.0.0, but a bad GitHub merge caused this fix to drop. I'll get this live for v3.1.0.

[AnashOommen]

Fixed in v4.0.0.