docs: .bind changes

Author: misterjoshua

Diff for: docs/core/tracer.md

@@ -143,8 +143,11 @@ You can quickly start by importing the `Tracer` class, initialize it outside the
     }
      
     export const handlerClass = new Lambda();
-    export const handler = handlerClass.handler;
+    export const handler = handlerClass.handler.bind(handlerClass); // (1)
     ```
+
+    1. Binding your handler method allows your handler to access `this`.
+
 === "Manual"
 
     ```typescript hl_lines="6 8-9 12-13 19 22 26 28"
@@ -253,8 +256,11 @@ You can trace other Class methods using the `captureMethod` decorator or any arb
     }
      
     export const myFunction = new Lambda();
-    export const handler = myFunction.handler; 
+    export const handler = myFunction.handler.bind(myFunction); // (1)
     ```
+
+    1. Binding your handler method allows your handler to access `this`.
+
 === "Manual"
 
     ```typescript hl_lines="6 8-9 15 18 23 25"

Diff for: packages/tracer/src/Tracer.ts

@@ -67,7 +67,7 @@ import { Segment, Subsegment } from 'aws-xray-sdk-core';
  * }
  * 
  * export const handlerClass = new Lambda();
- * export const handler = handlerClass.handler; 
+ * export const handler = handlerClass.handler.bind(handlerClass);
  * ```
  * 
  * ### Functions usage with manual instrumentation
@@ -334,7 +334,7 @@ class Tracer extends Utility implements TracerInterface {
    * }
    * 
    * export const handlerClass = new Lambda();
-   * export const handler = handlerClass.handler; 
+   * export const handler = handlerClass.handler.bind(handlerClass);
    * ```
    * 
    * @decorator Class

Diff for: packages/tracer/tests/unit/Tracer.test.ts

@@ -881,7 +881,8 @@ describe('Class: Tracer', () => {
 
       // Act / Assess
       const lambda = new Lambda('someValue');
-      expect(await lambda.handler({}, context, () => console.log('Lambda invoked!'))).toEqual('memberVariable:someValue');
+      const handler = lambda.handler.bind(lambda);
+      expect(await handler({}, context, () => console.log('Lambda invoked!'))).toEqual('memberVariable:someValue');
 
     });
   });