crypto/tls: Conn.Close should not override user's write deadline

[kozlovic]

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

$ go version
go version go1.16.2 darwin/amd64

Does this issue reproduce with the latest release?

Yes:

go/src/crypto/tls/conn.go

Line 1361 in 8fd0f83

c.SetWriteDeadline(time.Now().Add(time.Second * 5))

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

All

What did you do?

Set a write deadline of my liking, close a TLS connection.

What did you expect to see?

The close to block for only the user specified deadline.

What did you see instead?

The close blocks for 5 seconds.

The library should not override the user write deadline, or add a field in tls.Config. See comments on existing issue: #31224 (comment)

[networkimprov]

cc @ianlancetaylor as possible proposal (adding a field in tls.Config)

cc @FiloSottile @katiehockman