make log file a CLI param; default to stdout if none is provided

main.go

@@ -3,6 +3,8 @@ package main
 import (
 	"os"
 
+	"github.com/spf13/viper"
+
 	"github.com/vulcanize/vulcanizedb/cmd"
 
 	"github.com/sirupsen/logrus"
@@ -12,13 +14,18 @@ func main() {
 	logrus.SetFormatter(&logrus.TextFormatter{
 		FullTimestamp: true,
 	})
-	file, err := os.OpenFile("vulcanizedb.log",
-		os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
-	if err == nil {
-		logrus.SetOutput(file)
+	logfile := viper.GetString("logfile")
+	if logfile != "" {
+		file, err := os.OpenFile(logfile,
+			os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0666)
+		if err == nil {
+			logrus.SetOutput(file)
+		} else {
+			logrus.SetOutput(os.Stdout)
+			logrus.Info("Failed to log to file, using default stdout")
+		}
 	} else {
-		logrus.Info("Failed to log to file, using default stderr")
+		logrus.SetOutput(os.Stdout)
 	}
-
 	cmd.Execute()
 }