pub_sub: go: set publisher sleep to 1 second (#891)

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.

Signed-off-by: Paško Zdilar <pasko.zdilar@meshmind.io>

pub_sub/go/http/checkout/app.go

@@ -45,6 +45,6 @@ func main() {
 
 		fmt.Println("Published data:", order)
 
-		time.Sleep(1000)
+		time.Sleep(time.Second)
 	}
 }

pub_sub/go/sdk/checkout/app.go

@@ -33,6 +33,6 @@ func main() {
 
 		fmt.Println("Published data:", order)
 
-		time.Sleep(1000)
+		time.Sleep(time.Second)
 	}
 }