Rename constants to make them more idiomatic Go

groupby.go

@@ -11,10 +11,10 @@ import (
 )
 
 const (
-	GROUPBY_VERSION    = "0.1.0"
-	SUBDIRECTORY_INNER = "├──"
-	SUBDIRECTORY_PIPE  = "│"
-	SUBDIRECTORY_LINK  = "└──"
+	Version           = "0.1.0"
+	SubdirectoryInner = "├──"
+	SubdirectoryPipe  = "│"
+	SubdirectoryLink  = "└──"
 )
 
 var (
@@ -160,7 +160,7 @@ func main() {
 	flag.Parse()
 
 	if version {
-		fmt.Println("groupby ", GROUPBY_VERSION, " - Group files and directories by the date they were created or modified")
+		fmt.Println("groupby ", Version, " - Group files and directories by the date they were created or modified")
 		fmt.Println("By Zikani Nyirenda Mwase ")
 		os.Exit(0)
 	}

printing_visitor.go

@@ -29,9 +29,9 @@ func (p *PrintingVisitor) Visit(n *Node, depth int) {
 		}
 	}
 
-	prefix := SUBDIRECTORY_INNER
+	prefix := SubdirectoryInner
 	if !n.HasNext() {
-		prefix = SUBDIRECTORY_LINK
+		prefix = SubdirectoryLink
 	}
 
 	filename := FileNameByDepth(n.FileName, depth)

tree.go

@@ -20,7 +20,7 @@ func NewTree(directory string, maxDepth int) *Tree {
 	year, month, day := GetYMD(directory)
 	dirPath, err := filepath.Abs(directory)
 	if err != nil {
-		log.Fatal(err)
+		panic(err)
 	}
 	return &Tree{
 		Root:           NewNode(dirPath, year, month, day),