Saving off entry string for use in panic

as the reader is not seekable and without this the panic string is
always empty 🙀

entry.go

@@ -88,10 +88,13 @@ func (entry *Entry) log(level Level, msg string) {
 		entry.Logger.mu.Unlock()
 	}
 
+	var panicBuf bytes.Buffer
+	teeOut := io.TeeReader(reader, &panicBuf)
+
 	entry.Logger.mu.Lock()
 	defer entry.Logger.mu.Unlock()
 
-	_, err = io.Copy(entry.Logger.Out, reader)
+	_, err = io.Copy(entry.Logger.Out, teeOut)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to write to log, %v\n", err)
 	}
@@ -100,7 +103,7 @@ func (entry *Entry) log(level Level, msg string) {
 	// panic() to use in Entry#Panic(), we avoid the allocation by checking
 	// directly here.
 	if level <= PanicLevel {
-		panic(reader.String())
+		panic(panicBuf.String())
 	}
 }
 

examples/basic/basic.go

@@ -12,6 +12,17 @@ func init() {
 }
 
 func main() {
+	defer func() {
+		err := recover()
+		if err != nil {
+			log.WithFields(logrus.Fields{
+				"omg":    true,
+				"err":    err,
+				"number": 100,
+			}).Fatal("The ice breaks!")
+		}
+	}()
+
 	log.WithFields(logrus.Fields{
 		"animal": "walrus",
 		"size":   10,
@@ -23,7 +34,7 @@ func main() {
 	}).Warn("The group's number increased tremendously!")
 
 	log.WithFields(logrus.Fields{
-		"omg":    true,
+		"animal": "orca",
-		"number": 100,
+		"size":   9009,
-	}).Fatal("The ice breaks!")
+	}).Panic("It's over 9000!")
 }