nestjs module is not injected properly

I created new module in nest using the command nest g module UserModule

src/user-module/user.resolver.ts is –

import { Query, Resolver } from '@nestjs/graphql';
import { UserService } from './user.service';

export class UserResolver {
  
  constructor (private readonly user: UserService) {
   this.user = user; 
  }

  @Query('users')
  async users() {
    return this.user.getUsers();
  }
}

then src/user-module/user-module.module.ts is –

import { Module } from '@nestjs/common';
import { UserResolver } from './user.resolver';
import { UserService } from './user.service';
import { PrismaService } from './prisma.services';

@Module({
  providers: [UserResolver, UserService, PrismaService]
})

export class UserModuleModule {}

the file src/user-module/user.service.ts –

import { Injectable } from "@nestjs/common";
import { PrismaService } from "./prisma.services";
import { User } from "src/graphql";

@Injectable()
export class UserService {
  constructor(private readonly prisma: PrismaService) {

  }

  async getUsers(): Promise<User[]> {
    return this.prisma.prismaUsers.findMany({})
  }
}

the src/user-module/prisma.services.ts –

import { Injectable, OnModuleInit } from '@nestjs/common';
import { PrismaClient } from '@prisma/client';

@Injectable()
export class PrismaService extends PrismaClient implements OnModuleInit {
  async onModuleInit() {
    await this.$connect();
  }
}

I started the service with npm start. I queried the service using below command –

query {
   users {
     id
     name
     email
   }
}

I get the below error –

[Nest] 24682 – 09/09/2023, 10:59:34 AM ERROR [ExceptionsHandler] Cannot read properties of undefined (reading’getUsers’)
TypeError: Cannot read properties of undefined (reading ‘getUsers’)
at UserResolver.users (/home/raj/Coding/ts/prisma-gql-express-demo/src/user-module/user.resolver.ts:12:22)
at /home/raj/Coding/ts/prisma-gql-express-demo/node_modules/@nestjs/core/helpers/external-context-creator.js:69:29
at InterceptorsConsumer.intercept (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/@nestjs/core/interceptors/interceptors-consumer.js:12:20)
at target (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/@nestjs/core/helpers/external-context-creator.js:74:60)
at Object.users (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/@nestjs/core/helpers/external-proxy.js:9:30)
at field.resolve (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/@apollo/server/src/utils/schemaInstrumentation.ts:82:22)
at executeField (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/graphql/execution/execute.js:492:20)
at executeFields (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/graphql/execution/execute.js:414:22)
at executeOperation (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/graphql/execution/execute.js:344:14)
at execute (/home/raj/Coding/ts/prisma-gql-express-demo/node_modules/graphql/execution/execute.js:136:20)

What is wrong with my injection and why it is not working ?
my complete code is here in github.
I seen this stackoverflow but my error seems to be due to different.