ConcurrentDictionary.GetOrAdd may run its factory more than once when asked at the same time, and each run started a
download: five clients asking at once for a new file made three upstream requests in one run of
Clients_asking_at_once_share_one_download. The factory now makes a Lazy, of which only the one kept is ever started,
and a download that begins just after another cached the file uses it.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw
thepraandClaude Opus 5.5
a4ced664cf