What version of Go are you using (go version)?

$ go version
go version go1.13.1 darwin/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

macOS 10.14.6 (18G6020)

What did you do?

Call Close() on a tls.Conn

What did you expect to see?

The call to Close() to not block, or documentation on the observed behavior

What did you see instead?

Rarely, Close() hangs indefinitely unless I also set a write deadline on the connection.

It's understandable as the TLS conn tries to send a close alert before closing the connection, but it's not clearly stated in the docs, and I wrongly assumed tls.Conn to have the same behavior as the underlying connection. As far as I can tell tls.Conn is the only type to implement the net.Conn interface in the std library to require a wrote deadline not to let Close block indefinitely. Afaict Read has the same "issue" in that it automagically performs the handshake first, with the aggravating factor that having to set a write deadline not to let Read block is even more unintuitive.