Update notes

learn_go_with_tests/dependency_injection/greet.go

@@ -17,7 +17,7 @@ func Greet(writer io.Writer, name string) {
 
 // Here you can see that since now our greeter function takes an object that
 // implements the io.Writer interface we can now pass an object like the http.ResponseWriter
-// to it.
+// to it. DI let's us reuse our code in a new context.
 func MyGreeterHandler(w http.ResponseWriter, r *http.Request) {
 	Greet(w, "world")
 }