var signer = new AWS4RequestSigner("accessKey", "secretKey");
    var content = new StringContent("{...}", Encoding.UTF8, "application/json");
    var request = new HttpRequestMessage {
        Method = HttpMethod.Get,
        RequestUri = new Uri("https://apigateway.execute-api.us-west-2.amazonaws.com/Prod/api/data"),
        Content = content
    };

    request = await signer.Sign(request, "execute-api", "us-west-2");

    var client = new HttpClient();
    var response = await client.SendAsync(request);

    var responseStr = await response.Content.ReadAsStringAsync();

{
  "access_key": "...",
  "secret_key": "...",
  "service": "execute-api",
  "region": "us-west-2",
  "request_uri": ""https://apigateway.execute-api.us-west-2.amazonaws.com/Prod/api/data",
  "json": "{...}"
}