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doc: add note about missing lock in sample code

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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>
This commit is contained in:
Ferenc Szabo 2020-06-25 11:12:50 +02:00 committed by Rob Pike
parent 8c521739f2
commit c4fd3f6ff6
1 changed files with 8 additions and 4 deletions
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doc/effective_go.html
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@ -2336,10 +2336,9 @@ of the request from the client.
</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 @@ func (ctr *Counter) ServeHTTP(w http.ResponseWriter, req *http.Request) {
<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>