fasthttp: increase connection pool size for postgresql (#3344)

Round 15 results suggest that the connection pool size is too small
for 512 concurrent requests. Double the size of the connection pool
and let's see how it performs in the Round 16.

frameworks/Go/fasthttp/src/server-postgresql/server.go

@@ -26,7 +26,7 @@ func main() {
 	flag.Parse()
 
 	var err error
-	maxConnectionCount := runtime.NumCPU() * 2
+	maxConnectionCount := runtime.NumCPU() * 4
 	if db, err = initDatabase("localhost", "benchmarkdbuser", "benchmarkdbpass", "hello_world", 5432, maxConnectionCount); err != nil {
 		log.Fatalf("Error opening database: %s", err)
 	}