add ErrInvalidScheme when HTTP is used

HTTP can result in silent failure, as Cloud Run will redirect to HTTPS, which
in turn is a 200 for the HTML content

client.go

@@ -5,12 +5,18 @@ package logs
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
+	"net/url"
 	"time"
 )
 
+// ErrInvalidScheme is returned when HTTP is used, which results in a silent failure
+// due to Cloud Run's redirection of HTTP -> HTTPs.
+var ErrInvalidScheme = errors.New("Client.URL must be HTTPS, not HTTP")
+
 // Alert represents configuration for performing alerting.
 type Alert struct {
 	// CreatedAt is a timestamp indicating when the alert was created. This field is read-only.
@@ -930,6 +936,17 @@ func (e Error) Error() string {
 func call(client *http.Client, authToken, endpoint, method string, in, out interface{}) error {
 	var body io.Reader
 
+	// parse the URL
+	u, err := url.Parse(endpoint)
+	if err != nil {
+		return fmt.Errorf("parsing url: %w", err)
+	}
+
+	// ensure HTTPS
+	if u.Scheme == "http" {
+		return ErrInvalidScheme
+	}
+
 	// default client
 	if client == nil {
 		client = http.DefaultClient

client_test.go

@@ -2,6 +2,7 @@ package logs_test
 
 import (
 	"os"
+	"strings"
 	"testing"
 
 	"github.com/apex/logs"
@@ -24,3 +25,14 @@ func TestService_GetProjects(t *testing.T) {
 	assert.NotEmpty(t, p.Description)
 	assert.NotEmpty(t, p.Name)
 }
+
+// Test erroring on HTTP.
+func TestHTTP(t *testing.T) {
+	c := logs.Client{
+		URL:       strings.Replace(os.Getenv("URL"), "https://", "http://", 1),
+		AuthToken: os.Getenv("AUTH_TOKEN"),
+	}
+
+	_, err := c.GetProjects()
+	assert.EqualError(t, err, "Client.URL must be HTTPS, not HTTP")
+}