Updating writeJSON helper method replacing json.Marshal() by json.MarshalIndent() method to improve responses readability. Updating README adding Performance sub-section.

README.md

@@ -71,4 +71,11 @@ A few other important things to mention :
 
 - Encoding of nested objects is supported. So, for example, if you have a slice of structs in Go that will encode to an *array of objects* in JSON.
 - Channels, functions and **complex** number types cannot be encoded. If you try to do so, you'll get a **json.UnsupportedTypeError** error at runtime.
-- Any pointer values will encode as *the value pointed to*.
+- Any pointer values will encode as *the value pointed to*.
+
+### Performance
+
+json.MarshalIndent() takes 65% longer to run and uses around 30% more memory than json.Marshal(), as well as making two more heap allocations. Those figures will change depending on what you're encoding, but they're fairly indicative of the performance impact.  
+
+For most applications this performance difference simply isn't something that you need to worry about. In real terms, we're talking about a few thousandths of a millisecond - and the improved readability of responses is probably worth this trade-off.  
+But if your API is operating in a very resource-constrained environment, or needs to manage extremely high levels of traffic, then this is worth being aware of and you may prefer to stick with using json.Marshal() instead.

cmd/api/helpers.go

@@ -49,8 +49,11 @@ http.ResponseWriter, the HTTP status code to send, the data to encode to JSON, a
 header map containing any additional HTTP headers we want to include in the response.
 */
 func (app *application) writeJSON(w http.ResponseWriter, status int, data any, headers http.Header) error {
-	// Encode the data to JSON, returning the error if there was one.
-	js, err := json.Marshal(data)
+	/*
+		Use the json.MarshalIndent() function so that whitespace is added to
+		the encoded JSON. Here we use no line prefix ("") and tab indents ("\t") for each element.
+	*/
+	js, err := json.MarshalIndent(data, "", "\t")
 	if err != nil {
 		return err
 	}