Quick http client with header override for authentication.

client.go

package main

import (
	"bytes"
	"fmt"
	"net/http"
	"net/url"
)

type TestClient struct {
	http.Client

	base *url.URL
	key  string
}

func New(base, key string) *TestClient {
	u, _ := url.Parse(base)
	c := &TestClient{
		base: u,
		key:  key,
	}
	c.Transport = c
	return c
}

func (c *TestClient) Echo(msg string) string {
	resp, err := c.Get("/anything?msg=" + msg)
	if err != nil {
		return err.Error()
	}
	defer resp.Body.Close()
	buf := &bytes.Buffer{}
	buf.ReadFrom(resp.Body)
	return resp.Status + " " + buf.String()
}

func (c *TestClient) RoundTrip(req *http.Request) (*http.Response, error) {
	req.URL = c.base.ResolveReference(req.URL)
	req.Header.Set("Authorization", c.key)
	return http.DefaultTransport.RoundTrip(req)
}

func main() {
	c := New("https://httpbin.org", "secret")
	fmt.Println(c.Echo("test"))
}