Unable to cast - 'CDSRuntime.SandboxWorker.SandboxOrganizationServiceWrapper' to type ..WebProxyClient<Microsoft.Xrm.Sdk.IOrganizationService

Question

I am trying to get access token from IOrganizationService inside custom workflow.

Below is the logic I'm using to retrieve IOrganisationService in custom workflow:

IWorkflowContext context = executionContext.GetExtension<IWorkflowContext>();
IOrganizationServiceFactory serviceFactory = executionContext.GetExtension<IOrganizationServiceFactory>();
_organizationService = serviceFactory.CreateOrganizationService(context.UserId);

I have tried getting Token through OrganizationServiceProxy by below code:

var proxy = (OrganizationServiceProxy) _organizationService;
var token = proxy.SecurityTokenResponse.Token;

which is also resulting in the same error.

What is the possible way here to get access token in this custom workflow?