docs: update README.md

- Added overview section.
- Added instructions on running the docker image.

README.md

@@ -1 +1,82 @@
 # Stock Ticker
+
+## Overview
+
+```
+$ curl http://stock-ticker.test/stockprice
+
+Symbol: MSFT
+
+Week       | Closing Price
+==========================
+2023-02-17 |   258.0600
+2023-02-10 |   263.1000
+2023-02-03 |   258.3500
+2023-01-27 |   248.1600
+2023-01-20 |   240.2200
+2023-01-13 |   239.2300
+2023-01-06 |   224.9300
+
+```
+This is a simple web service that prints the last 'N' weeks of closing stock prices for a particular stock.
+The data is retrieved from [Alpha Vantage's API](https://www.alphavantage.co/documentation/).
+
+The web service servers the following endpoints:
+
+- `/healthcheck` - Returns `200` if the server is up and running.
+- `/stockprice` - Prints the closing prices for the latest N weeks.
+
+### Alpha Vantage API Key
+
+Before running the web service you'll need to obtain an API key from Alpha Vantage.
+You can claim a free key from:
+
+https://www.alphavantage.co/support/#api-key
+
+### Required environment variables
+
+| Environment Variable | Description                                    | Example |
+|----------------------|------------------------------------------------|---------|
+| SYMBOL               | The symbol of the stock.                       | MSFT    |
+| NWEEKS               | Display the closing price for the last N weeks.| 7       |
+| APIKEY               | Your API key from Alpha Vantage.               |         |
+
+### Command line arguments
+
+| Argument | Description                                     | Default      |
+|----------|-------------------------------------------------|--------------|
+| address  | The address that the web server will listen on. | 0.0.0.0:8080 |
+
+## Running the docker image locally
+
+The docker image is published to the GitLab container registry [here](https://gitlab.com/dananglin/stock-ticker/container_registry/3916158).
+You can pull and run the docker image from the registry with the following command:
+
+```bash
+docker run --rm \
+    -d \
+    -e SYMBOL=MSFT \
+    -e NWEEKS=3 \
+    -e APIKEY=<YOUR_API_KEY> \
+    --publish 8080:8080 \
+    --name stock-ticker \
+    registry.gitlab.com/dananglin/stock-ticker:v0.1.0
+```
+
+Alternatively you can build and run the docker image locally.
+
+```bash
+git clone https://gitlab.com/dananglin/stock-ticker.git
+cd stock-ticker
+docker build -t stock-ticker .
+docker run --rm \
+    -d \
+    -e SYMBOL=MSFT \
+    -e NWEEKS=3 \
+    -e APIKEY=<YOUR_API_KEY> \
+    --publish 8080:8080 \
+    --name stock-ticker \
+    stock-ticker
+```
+
+Now you can go to http://localhost:8080/stockprice in your browser to view a table of the latest weekly closing stock prices for `MSFT`.