Add helper

helper.go

@@ -0,0 +1,36 @@
+package mastodon
+
+import (
+	"encoding/base64"
+	"net/http"
+	"os"
+)
+
+func Base64EncodeFileName(filename string) (string, error) {
+	file, err := os.Open(filename)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+
+	return Base64Encode(file)
+}
+
+func Base64Encode(file *os.File) (string, error) {
+	fi, err := file.Stat()
+	if err != nil {
+		return "", err
+	}
+
+	d := make([]byte, fi.Size())
+	_, err = file.Read(d)
+	if err != nil {
+		return "", err
+	}
+
+	return "data:" + http.DetectContentType(d) +
+		";base64," + base64.StdEncoding.EncodeToString(d), nil
+}
+
+// String is a helper function to get the pointer value of a string.
+func String(v string) *string { return &v }