First (unsuccessful) attempt at day 7.1.

2018/internal/util/strings.go

@@ -0,0 +1,14 @@
+package util
+
+func ReverseString(s string) string {
+	runes := []rune(s)
+
+	i := 0
+	j := len(runes) - 1
+	for i < j {
+		runes[i], runes[j] = runes[j], runes[i]
+		i++
+		j--
+	}
+	return string(runes)
+}