func (u *URL) JoinPath(elem ...string) *URL

JoinPath returns a new URL with the provided path elements joined to any existing path and the resulting path cleaned of any ./ or ../ elements. Any sequences of multiple / characters will be reduced to a single /. Path elements must already be in escaped form, as produced by PathEscape.

Example 
{
	u, err := url.Parse("https://example.com/foo/bar")
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println(u.JoinPath("baz", "qux"))

}

Output:

https://example.com/foo/bar/baz/qux