github.com/mattn/go-runewidth supports zero-width joiners now.

util.go

@@ -51,6 +51,9 @@ var (
 
 // Package initialization.
 func init() {
+	// We'll use zero width joiners.
+	runewidth.ZeroWidthJoiner = true
+
 	// Initialize the predefined input field handlers.
 	InputFieldInteger = func(text string, ch rune) bool {
 		if text == "-" {