Consolidate serverless configurations into one place (#105)

* Update README.md

* Update README.md

Author: tianchu

README.md

@@ -10,104 +10,11 @@ Datadog Lambda Library for Go enables enhanced Lambda metrics, distributed traci
 
 ## Installation
 
-Follow the installation instructions [here](https://docs.datadoghq.com/serverless/installation/go/).
+Follow the [installation instructions](https://docs.datadoghq.com/serverless/installation/go/), and view your function's enhanced metrics, traces and logs in Datadog.
 
-## Enhanced Metrics
+## Configurations
 
-Once [installed](#installation), you should be able to view enhanced metrics for your Lambda function in Datadog.
-
-Check out the official documentation on [Datadog Lambda enhanced metrics](https://docs.datadoghq.com/integrations/amazon_lambda/?tab=go#real-time-enhanced-lambda-metrics).
-
-## Custom Metrics
-
-Once [installed](#installation), you should be able to submit custom metrics from your Lambda function.
-
-Check out the instructions for [submitting custom metrics from AWS Lambda functions](https://docs.datadoghq.com/integrations/amazon_lambda/?tab=go#custom-metrics).
-
-## Tracing
-
-Set the `DD_TRACE_ENABLED` environment variable to `true` to enable Datadog tracing. When Datadog tracing is enabled, the library will inject a span representing the Lambda's execution into the context object. You can then use the included `dd-trace-go` package to create additional spans from the context or pass the context to other services. For more information, see the [dd-trace-go documentation](https://godoc.org/gopkg.in/DataDog/dd-trace-go.v1/ddtrace).
-
-```go
-import (
-  "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer"
-  httptrace "gopkg.in/DataDog/dd-trace-go.v1/contrib/net/http"
-)
-
-func handleRequest(ctx context.Context, ev events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
-  // Trace an HTTP request
-  req, _ := http.NewRequestWithContext(ctx, "GET", "https://www.datadoghq.com", nil)
-  client := http.Client{}
-  client = *httptrace.WrapClient(&client)
-  client.Do(req)
-
-  // Create a custom span
-  s, _ := tracer.StartSpanFromContext(ctx, "child.span")
-  time.Sleep(100 * time.Millisecond)
-  s.Finish()
-}
-```
-
-You can also use the injected span to [connect your logs and traces](https://docs.datadoghq.com/tracing/connect_logs_and_traces/go/).
-
-```go
-func handleRequest(ctx context.Context, ev events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
-  currentSpan, _ := tracer.SpanFromContext(ctx)
-  log.Printf("my log message %v", currentSpan)
-}
-```
-
-If you are also using AWS X-Ray to trace your Lambda functions, you can set the `DD_MERGE_XRAY_TRACES` environment variable to `true`, and Datadog will merge your Datadog and X-Ray traces into a single, unified trace.
-
-### Trace Context Extraction
-
-To link your distributed traces, datadog-lambda-go looks for the `x-datadog-trace-id`, `x-datadog-parent-id` and `x-datadog-sampling-priority` trace `headers` in the Lambda event payload.
-If the headers are found it will set the parent trace to the trace context extracted from the headers.
-
-It is possible to configure your own trace context extractor function if the default extractor does not support your event.
-
-```go
-myExtractorFunc := func(ctx context.Context, ev json.RawMessage) map[string]string {
-    // extract x-datadog-trace-id, x-datadog-parent-id and x-datadog-sampling-priority.
-}
-
-cfg := &ddlambda.Config{
-    TraceContextExtractor: myExtractorFunc,
-}
-ddlambda.WrapFunction(handler, cfg)
-```
-
-A more complete example can be found in the `ddlambda_example_test.go` file.
-
-## Environment Variables
-
-### DD_FLUSH_TO_LOG
-
-Set to `true` (recommended) to send custom metrics asynchronously (with no added latency to your Lambda function executions) through CloudWatch Logs with the help of [Datadog Forwarder](https://github.com/DataDog/datadog-serverless-functions/tree/master/aws/logs_monitoring). Defaults to `false`. If set to `false`, you also need to set `DD_API_KEY` and `DD_SITE`.
-
-### DD_API_KEY
-
-If `DD_FLUSH_TO_LOG` is set to `false` (not recommended), the Datadog API Key must be defined.
-
-### DD_SITE
-
-If `DD_FLUSH_TO_LOG` is set to `false` (not recommended), you must set `DD_SITE`. Possible values are `datadoghq.com`, `datadoghq.eu`, `us3.datadoghq.com`, `us5.datadoghq.com`, and `ddog-gov.com`. The default is `datadoghq.com`.
-
-### DD_LOG_LEVEL
-
-Set to `debug` enable debug logs from the Datadog Lambda Library. Defaults to `info`.
-
-### DD_ENHANCED_METRICS
-
-Generate enhanced Datadog Lambda integration metrics, such as, `aws.lambda.enhanced.invocations` and `aws.lambda.enhanced.errors`. Defaults to `true`.
-
-### DD_TRACE_ENABLED
-
-Initialize the Datadog tracer when set to `true`. Defaults to `false`.
-
-### DD_MERGE_XRAY_TRACES
-
-If you are using both X-Ray and Datadog tracing, set this to `true` to merge the X-Ray and Datadog traces. Defaults to `false`.
+See the [advanced configuration options](https://docs.datadoghq.com/serverless/configuration) to tag your telemetry, capture request/response payloads, filter or scrub sensitive information from logs or traces, and more.
 
 ## Opening Issues