refactor: change project structure and package name

pkg/chart/font.go

@@ -0,0 +1,29 @@
+package chart
+
+import (
+	"github.com/d-Rickyy-b/go-chart-x/v2/pkg/roboto"
+	"sync"
+
+	"github.com/golang/freetype/truetype"
+)
+
+var (
+	_defaultFontLock sync.Mutex
+	_defaultFont     *truetype.Font
+)
+
+// GetDefaultFont returns the default font (Roboto-Medium).
+func GetDefaultFont() (*truetype.Font, error) {
+	if _defaultFont == nil {
+		_defaultFontLock.Lock()
+		defer _defaultFontLock.Unlock()
+		if _defaultFont == nil {
+			font, err := truetype.Parse(roboto.Roboto)
+			if err != nil {
+				return nil, err
+			}
+			_defaultFont = font
+		}
+	}
+	return _defaultFont, nil
+}