url.go

package main

import (
	"fmt"
	"net/url"

	"github.com/pkg/errors"
)

func main() {

	fmt.Println(mustCombine("https://www.example.com/foo/bar", "example"))
	fmt.Println(mustCombine("https://www.example.com/foo/bar", "/example"))
	fmt.Println(mustCombine("https://www.example.com/foo/bar/", "example"))
	fmt.Println(mustCombine("https://www.example.com/foo/bar/", "/example"))

}

func mustCombine(baseStr, suffixStr string) *url.URL {
	u, err := combine(baseStr, suffixStr)
	if err != nil {
		panic(err)
	}
	return u
}

func combine(baseStr, suffixStr string) (*url.URL, error) {

	// parse base URL
	base, err := url.Parse(baseStr)
	if err != nil {
		return nil, errors.Wrap(err, "bad base URL")
	}

	// parse suffix
	suffix, err := url.Parse(suffixStr)
	if err != nil {
		return nil, errors.Wrap(err, "bad suffix")
	}

	return base.ResolveReference(suffix), nil

}