[release-branch.go1.11] crypto/tls: make ConnectionState.ExportKeyingMaterial a method
The unexported field is hidden from reflect based marshalers, which
would break otherwise. Also, make it return an error, as there are
multiple reasons it might fail.
Fixes #27131
Change-Id: I92adade2fe456103d2d5c0315629ca0256953764
Reviewed-on: https://go-review.googlesource.com/130535
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit
240cb4c75fbe969364edb1a7f7ebd2d827831d34)
Reviewed-on: https://go-review.googlesource.com/130655