pub_sub: go: set publisher sleep to 1 second

[paskozdilar]

Description

The current implementation calls time.Sleep(1000) with untyped literal 1000, which is interpreted as 1000 nanoseconds, or 1 millisecond.

This commit changes the sleep duration to proper typed constant time.Second, which corresponds to the sleep time of other language examples.

Issue reference

This issue will close #890.

Checklist

I have completed all the tasks:

• The quickstart code compiles correctly
• You've tested new builds of the quickstart if you changed quickstart code
• You've updated the quickstart's README if necessary
• If you have changed the steps for a quickstart be sure that you have updated the automated validation accordingly. All of our quickstarts have annotations that allow them to be executed automatically as code. For more information see mechanical-markdown. For user guide with examples see Examples.

[rabollin]

Looks good, specifying the correction duration will be more readable, the sleep duration will be exact one sec.

[msfussell]

LGTM