Please configure a Postgresql instance in docker to accept requests on port 4121.
### 1. Install Docker
If you don't already have Docker installed on your machine, you can download it from the official Docker website [here](https://www.docker.com/products/docker-desktop).

### 2. Open a terminal window or command prompt
You'll need to open a terminal window or command prompt to run the following commands.

### 3. Pull the PostgreSQL image
Use the following command to pull the PostgreSQL image from Docker Hub:

```
docker pull postgres
```


### 4. Create a Docker container with the PostgreSQL image
Use the following command to create a Docker container with the PostgreSQL image, setting the PostgreSQL password to mysecretpassword and mapping port 4121 on the host machine to port 5432 in the container:

```
docker run --name my-postgres -e POSTGRES_PASSWORD=mysecretpassword -p 4121:5432 -d postgres
```

### 5. Verify that the container is running
Use the following command to verify that the container is running:

```
docker ps
```


### 6. Connect to the PostgreSQL instance
Use the following command to connect to the PostgreSQL instance running in the Docker container:


```
psql -h localhost -p 4121 -U postgres
```


### 7. Execute SQL queries
Once you're connected to the PostgreSQL instance, you can execute SQL queries as you would with any other PostgreSQL database.
Create docker compose file for Postgres instance
To create a Docker Compose file for a PostgreSQL instance, first create a new file named `docker-compose.yml` in a directory of your choice. Open the file with a text editor and paste the following contents:
```yaml
version: 3.9

services:
  postgres:
    image: postgres
    container_name: my-postgres
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: mysecretpassword
      POSTGRES_DB: mydatabase
    ports:
      - 4121:5432
    volumes:
      - postgres-data:/var/lib/postgresql/data

volumes:
  postgres-data:
```

This configuration creates a PostgreSQL service using the official PostgreSQL image. It sets the PostgreSQL username, password, and database name using environment variables. The container maps port 4121 on the host machine to port 5432 inside the container. A named volume, postgres-data, is used to store the PostgreSQL data, ensuring that it persists even if the container is removed.

To start the PostgreSQL instance using Docker Compose, open a terminal window or command prompt in the directory where you created the docker-compose.yml file and run:

```bash
docker-compose up -d
```

This command starts the services defined in the docker-compose.yml file in detached mode, so you can continue using the terminal or command prompt. To stop the services and remove the containers, run:

```bash
docker-compose down
```

Remember to replace mysecretpassword with a secure password of your choice for the PostgreSQL instance.