Does golang's net/http.Client set a default Host header? Nope!

host_header_test.go

package headers

import (
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/stretchr/testify/require"
)

func TestHostHeader(t *testing.T) {
	handler := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
		require.Equal(t, "localhost", req.Header.Get("Host"))
		w.WriteHeader(204)
	})
	server := httptest.NewServer(handler)
	resp, err := server.Client().Get(server.URL + "/whatever")
	require.NoError(t, err)
	require.Equal(t, 204, resp.StatusCode)
}