code: public void terminateWorkflow(String workflowId, String reason) {
          Preconditions.checkArgument(StringUtils.isNotBlank(workflowId), "workflow id cannot be blank");
          stub.terminateWorkflow(WorkflowServicePb.TerminateWorkflowRequest.newBuilder()
                  .setWorkflowId(workflowId)
                  .setReason(reason)
                  .build()
          );
      }
docs: Terminates the execution of the given workflow instance
  
  @param workflowId the id of the workflow to be terminated
  @param reason     the reason to be logged and displayed