context: document that WithValue returns a derived context
Also replace "copy of parent" with "derived context" in doc comments.
Fixes #68923
Change-Id: I319c1594f390e35b32b4e58ee979927bb84bfdf9
Reviewed-on: https://go-review.googlesource.com/c/go/+/606555 Reviewed-by: Sameer Ajmani <sameer@golang.org> Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Sameer Ajmani <sameer@golang.org>
Commit-Queue: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
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