more info around tracing

Author: erickhun

README.md

@@ -23,4 +23,25 @@ If you wish to see more logs, simply set the `LOG_LEVEL` to the desired level. H
 | NOTICE | Logs that track the general flow of the application. This is the default level |   |
 | WARNING | Logs that highlight an abnormal or unexpected event in the application flow, but do not otherwise cause the application execution to stop.  |   |
 | ERROR |  Logs that highlight when the current flow of execution is stopped due to a failure. These should indicate a failure in the current activity, not an application-wide failure. |   |
-| CRITICAL  | Logs that describe an unrecoverable application or system crash, or a catastrophic failure that requires immediate attention.  |   |
+| CRITICAL  | Logs that describe an unrecoverable application or system crash, or a catastrophic failure that requires immediate attention.  |   |
+
+
+## Add traces to log
+
+A great feature of Datadog is to correlate traces and logs to make troubleshooting easier. 
+
+To take advantage of this, you will need to:
+- install the `dd-trace` package 
+- import it and init it with `logInjection:true`. 
+- BuffLog will append automatically the traces to the logs (only within a request)
+
+```js
+// make sure to put those lines at the very beginning of your service
+import tracer from "dd-trace";
+tracer.init({
+    //  will automatically append the traces to BuffLog
+    logInjection: true
+
+    // ... all other options...
+});
+```