doc: add note about missing lock in sample code
The sample code in 'Interfaces and methods' section contains a
data race. Handlers are served concurrently. The handler does write
and read operations; `go test -race` would fail (with concurrent
requests). Since the doc is frozen and the code remains less
cluttered without locks/atomic, don't change the sample code.
Change-Id: I654b324d2f0b7f48497822751907c7d39e2f0e3d
Reviewed-on: https://go-review.googlesource.com/c/go/+/239877
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/doc/effective_go.html b/doc/effective_go.html
index 9be6bc7..7620402 100644
--- a/doc/effective_go.html
+++ b/doc/effective_go.html
@@ -2336,10 +2336,9 @@
</p>
<p>
For brevity, let's ignore POSTs and assume HTTP requests are always
-GETs; that simplification does not affect the way the handlers are
-set up. Here's a trivial but complete implementation of a handler to
-count the number of times the
-page is visited.
+GETs; that simplification does not affect the way the handlers are set up.
+Here's a trivial implementation of a handler to count the number of times
+the page is visited.
</p>
<pre>
// Simple counter server.
@@ -2355,6 +2354,11 @@
<p>
(Keeping with our theme, note how <code>Fprintf</code> can print to an
<code>http.ResponseWriter</code>.)
+In a real server, access to <code>ctr.n</code> would need protection from
+concurrent access.
+See the <code>sync</code> and <code>atomic</code> packages for suggestions.
+</p>
+<p>
For reference, here's how to attach such a server to a node on the URL tree.
</p>
<pre>
