How to write graphql subscriptions

1. Write Graphql Service

// services.graqphl

"""
 Subscription event for timer
"""
enum TimeTrackerPubSubEvents {
    TimeTrackerCreated
    TimeTrackerUpdated
    TimeTrackerConfigurationUpdate
}

// timerecord.graphql
extend type Subscription {
  SubscribeToTimeTracker(orgNameFilter: string, userId: String): TimeRecord
}


// resolvers

import {withFilter} from 'graphql-subscriptions';

export const resolver = (options) => ({
  ....
  Subscription: {
    SubscribeToOrganizationContext: {
      subscribe: withFilter(
        () =>
          options.pubsub.asyncIterator([
            ITimeRecordPubSubEvents.TimeRecordCreated,
            ITimeRecordPubSubEvents.TimeRecordUpdated,
          ]),
        async (payload, variables, context: {}) =>
          payload.SubscribeToOrganizationContext.orgId === variables.orgNameFilter &&
          payload.SubscribeToOrganizationContext.userId === variables.userId,
      ),
    },
  },

})



/// service file


  public async createTimeRecord(userId: string, orgId: string, request: ITimeRecordRequest) {
    const data = await this.timeRecordRepository.createTimeRecord(userId, orgId, request);
    this.pubsub.publish(ITimeRecordPubSubEvents.TimeRecordCreated, { SubscribeToTimeTracker: data });
    return data;
  }