playground/socket: fix message buffering
playground/socket: fix message buffering

Use time.After to avoid the finnicky antics of
correctly resetting a time.Timer.

Fixes golang/go#13749

Change-Id: I3f1ed17a31d981996e2bb7a8155c3ba0ec723c7d
Reviewed-on: https://go-review.googlesource.com/19942
Reviewed-by: Dmitry Vyukov <05e8181be3150e47da8fe2e1f18d381c75496ff4@google.com>

golang/tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools,golang/tools,golang/tools,golang/tools,syreclabs/go-tools,syreclabs/go-tools,golang/tools