go.blog: fixed date on oscon
go.blog: fixed date on oscon

LGTM=iant
R=r, iant
CC=golang-codereviews
https://codereview.appspot.com/115850043

d0f/go-zh.blog,bryanxu/go-zh.blog,webfd/go-zh.blog,bryanxu/go-zh.blog,d0f/go-zh.blog,webfd/go-zh.blog