Set Host header in HTTP provider request

pkg/provider/http/http.go

@@ -7,6 +7,7 @@ import (
 	"hash/fnv"
 	"io"
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/cenkalti/backoff/v4"
@@ -149,8 +150,12 @@ func (p *Provider) fetchConfigurationData() ([]byte, error) {
 	}
 
 	for k, v := range p.Headers {
+		if strings.EqualFold(k, "Host") {
+			req.Host = v
+		} else {
 			req.Header.Set(k, v)
 		}
+	}
 
 	res, err := p.httpClient.Do(req)
 	if err != nil {

pkg/provider/http/http_test.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 	"time"
 
@@ -87,6 +88,7 @@ func TestProvider_fetchConfigurationData(t *testing.T) {
 			headers: map[string]string{
 				"Foo":  "bar",
 				"Bar":  "baz",
+				"Host": "localhost",
 			},
 			expData: []byte("{}"),
 			expErr:  require.NoError,
@@ -105,8 +107,12 @@ func TestProvider_fetchConfigurationData(t *testing.T) {
 				handlerCalled = true
 
 				for k, v := range test.headers {
+					if strings.EqualFold(k, "Host") {
+						assert.Equal(t, v, req.Host)
+					} else {
 						assert.Equal(t, v, req.Header.Get(k))
 					}
+				}
 
 				rw.WriteHeader(test.statusCode)
 				_, _ = rw.Write([]byte("{}"))