api: promote next to go1.11

Change-Id: Ib8fa0a12363993033201ff707c315f4030811f89
Reviewed-on: https://go-review.googlesource.com/120595
Run-TryBot: Andrew Bonventre <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: andybons