use a switch/case for get mime

mime/mime.go

@@ -1,16 +1,24 @@
 package mime
 
-func FromExtension(ext string) (string, bool) {
-	types := map[string]string{
-		"mp3":  "audio/mpeg",
-		"flac": "audio/x-flac",
-		"aac":  "audio/x-aac",
-		"m4a":  "audio/m4a",
-		"m4b":  "audio/m4b",
-		"ogg":  "audio/ogg",
-		"opus": "audio/ogg",
-		"wma":  "audio/x-ms-wma",
+func FromExtension(ext string) string {
+	switch ext {
+	case "mp3":
+		return "audio/mpeg"
+	case "flac":
+		return "audio/x-flac"
+	case "aac":
+		return "audio/x-aac"
+	case "m4a":
+		return "audio/m4a"
+	case "m4b":
+		return "audio/m4b"
+	case "ogg":
+		return "audio/ogg"
+	case "opus":
+		return "audio/ogg"
+	case "wma":
+		return "audio/x-ms-wma"
+	default:
+		return ""
 	}
-	v, ok := types[ext]
-	return v, ok
 }