This is a simple in-memory storage service that allows clients to add, delete, and retrieve key-value pairs via a REST API. The service also includes rate limiting functionality to limit the number of requests per second from a single IP address.

The API includes the following endpoints:

• POST /set: Add a new key-value pair to the storage. The request body should include a JSON object with the key and value fields. An optional expiration field can be included to set a time-to-live value for the key in seconds.
• DELETE /delete?key=: Delete the key-value pair with the specified key from the storage.
• GET /get?key=: Retrieve the value for the key with the specified key from the storage.
• GET /all: Retrieve all key-value pairs from the storage.

Object should be in the following format:

{
    "key": "key",
    "value": "value",
    "expiration": 60
}

as in this Entity struct:

// Entity represents a key-value pair in the in-memory storage.
type Entity struct {
	Key   string `json:"key"`
	Value string `json:"value"`
	// Expiration is the time in nanoseconds when the key-value pair will expire.
	Expiration int64 `json:"expiration"`
}

If a client exceeds the rate limit, the service will return a 429 Too Many Requests HTTP status code.

The service can be configured using the environment variables listed below:
SERVER_PORT server port, default 8080
RATE_LIMIT rate limit in requests per second, default 10
This value is used to calculate how many nanoseconds to wait between requests from a single IP address.

To build the service, run the following command:

go build -o in-memory-storage cmd/in-memory-storage/main.go

To run the service, use the following command:

./in-memory-storage

The service can also be run using Docker. To build the Docker image, use the following command:

docker build -t in-memory-storage .

To run the Docker container, use the following command:

docker run -p 8080:8080 in-memory-storage

To run the tests for the service, use the following command:

go test ./...