grpc_wait - Waits for a session to end.
  grpc_error_t grpc_wait(grpc_sessionid_t session_id)
  grpc_sessionid_t session_idThe grpc_wait() function waits for the specified session to end.
This function is MT-safe unless multiple wait functions wait the same sessions simultaneously.
If successful, GRPC_NO_ERROR is returned. In the case of an error, Error code is returned.
  GRPC_NOT_INITIALIZED  GRPC_INVALID_SESSION_ID  GRPC_COMMUNICATION_FAILED  GRPC_SESSION_FAILED  GRPC_TIMEOUT_NP  GRPC_OTHER_ERROR_CODE