When an HTTPS or tcpmux route listener is closed after a connection has been
resolved to it but before the handoff, Muxer.handle clears the deadline and
then sends on the closed accept channel. The recovered panic returns without
closing the connection, so the peer waits until its own read timeout.
Add a done channel and sync.Once to Listener. Close closes done and is
idempotent; handle and Accept select on accept/done, and a pending connection
is closed when done is closed. Connections already handed to Accept keep their
current ownership. Remove the PanicToError-based control flow.
Cover the pending handoff with net.Pipe and real TCP tests, plus an idempotent
Close test.
Fixes#5573
Reduced log level of "get hostname from http/https request error" to debug so that it won't overwhelms the log file when user is using apache/ngix as their own SSL backend
fatedier
Zeyu Dong
XNG