Clarify GC in structs example

Fixes #550

examples/structs/structs.go

@@ -14,8 +14,10 @@ type person struct {
 
 // `newPerson` constructs a new person struct with the given name.
 func newPerson(name string) *person {
-	// You can safely return a pointer to local variable
-	// as a local variable will survive the scope of the function.
+	// Go is a garbage collected language; you can safely
+	// return a pointer to a local variable - it will only
+	// be cleaned up by the garbage collector when there
+	// are no active references to it.
 	p := person{name: name}
 	p.age = 42
 	return &p

examples/structs/structs.hash

@@ -1,2 +1,2 @@
-80344041b9268370bb6c73190afb1269e26f52fe
-ex1J3oieEeo
+b50c1756bf9a2ea7f8853f7f7cb7a61d5efebfc3
+56SPo-L2nMN

public/structs

@@ -46,7 +46,7 @@ records.</p>
             
           </td>
           <td class="code leading">
-            <a href="https://go.dev/play/p/ex1J3oieEeo"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
+            <a href="https://go.dev/play/p/56SPo-L2nMN"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
           <pre class="chroma"><code><span class="line"><span class="cl"><span class="kn">package</span> <span class="nx">main</span></span></span></code></pre>
           </td>
         </tr>
@@ -88,8 +88,10 @@ records.</p>
         
         <tr>
           <td class="docs">
-            <p>You can safely return a pointer to local variable
-as a local variable will survive the scope of the function.</p>
+            <p>Go is a garbage collected language; you can safely
+return a pointer to a local variable - it will only
+be cleaned up by the garbage collector when there
+are no active references to it.</p>
 
           </td>
           <td class="code leading">