@Nullable
    private static String paramName(String token) {
        if (token.startsWith("{") && token.endsWith("}")) {
            final int beginIndex = token.charAt(1) == '*' ? 2 : 1;
            return token.substring(beginIndex, token.length() - 1);
        }

        if (token.startsWith(":")) {
            final int beginIndex = token.charAt(1) == '*' ? 2 : 1;
            return token.substring(beginIndex);
        }

        return null;
    }
Returns the name of the path parameter contained in the path element. If it contains no path parameter,
{@code null} is returned. e.g.
<ul>
  <li>{@code "{foo}"} -> {@code "foo"}</li>
  <li>{@code ":bar"} -> {@code "bar"}</li>
  <li>{@code "baz"} -> {@code null}</li>
  <li>{@code "{*foo}"} -> {@code "foo"}</li>
  <li>{@code ":*foo"} -> {@code "foo"}</li>
</ul>
core/src/main/java/com/linecorp/armeria/server/ParameterizedPathMapping.java