Factor out inttest logging setup into a separate package

integrationtests/tools/testlog/testlog.go

@@ -0,0 +1,41 @@
+package testlog
+
+import (
+	"flag"
+	"log"
+	"os"
+
+	"github.com/lucas-clemente/quic-go/internal/utils"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var (
+	logFileName string // the log file set in the ginkgo flags
+	logFile     *os.File
+)
+
+// read the logfile command line flag
+// to set call ginkgo -- -logfile=log.txt
+func init() {
+	flag.StringVar(&logFileName, "logfile", "", "log file")
+}
+
+var _ = BeforeEach(func() {
+	log.SetFlags(log.Ldate | log.Ltime | log.Lmicroseconds)
+
+	if len(logFileName) > 0 {
+		var err error
+		logFile, err = os.Create("./log.txt")
+		Expect(err).ToNot(HaveOccurred())
+		log.SetOutput(logFile)
+		utils.SetLogLevel(utils.LogLevelDebug)
+	}
+})
+
+var _ = AfterEach(func() {
+	if len(logFileName) > 0 {
+		_ = logFile.Close()
+	}
+})