create new func to avoid the bug on issue #61

examples_test.go

@@ -1,29 +1,30 @@
 package oauth_test
 
 import (
-	"fmt"
-	"os"
+  "fmt"
+  "os"
 
-	"github.com/cli/oauth"
+  "github.com/cli/oauth"
 )
 
 // DetectFlow attempts to initiate OAuth Device flow with the server and falls back to OAuth Web
 // application flow if Device flow seems unsupported. This approach isn't strictly needed for
 // github.com, as its Device flow support is globally available, but it enables logging in to
 // self-hosted GitHub instances as well.
 func ExampleFlow_DetectFlow() {
-	flow := &oauth.Flow{
-		Host:         oauth.GitHubHost("https://github.com"),
-		ClientID:     os.Getenv("OAUTH_CLIENT_ID"),
-		ClientSecret: os.Getenv("OAUTH_CLIENT_SECRET"), // only applicable to web app flow
-		CallbackURI:  "http://127.0.0.1/callback",      // only applicable to web app flow
-		Scopes:       []string{"repo", "read:org", "gist"},
-	}
+  host, err := oauth.NewGitHubHost("https://github.com")
+  flow := &oauth.Flow{
+    Host:         host,
+    ClientID:     os.Getenv("OAUTH_CLIENT_ID"),
+    ClientSecret: os.Getenv("OAUTH_CLIENT_SECRET"), // only applicable to web app flow
+    CallbackURI:  "http://127.0.0.1/callback",      // only applicable to web app flow
+    Scopes:       []string{"repo", "read:org", "gist"},
+  }
 
-	accessToken, err := flow.DetectFlow()
-	if err != nil {
-		panic(err)
-	}
+  accessToken, err := flow.DetectFlow()
+  if err != nil {
+    panic(err)
+  }
 
-	fmt.Printf("Access token: %s\n", accessToken.Token)
+  fmt.Printf("Access token: %s\n", accessToken.Token)
 }

oauth.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"strings"
 
 	"github.com/cli/oauth/api"
 	"github.com/cli/oauth/device"
@@ -24,6 +25,25 @@ type Host struct {
 	TokenURL      string
 }
 
+func NewGitHubHost(hostURL string) (*Host, error) {
+	base, err := url.Parse(strings.TrimSpace(hostURL))
+	if err != nil {
+		return nil, err
+	}
+
+	createURL := func(path string) string {
+		u := *base // Copy base URL
+		u.Path = path
+		return u.String()
+	}
+
+	return &Host{
+		DeviceCodeURL: createURL("/login/device/code"),
+		AuthorizeURL:  createURL("/login/oauth/authorize"),
+		TokenURL:      createURL("/login/oauth/access_token"),
+	}, nil
+}
+
 // GitHubHost constructs a Host from the given URL to a GitHub instance.
 func GitHubHost(hostURL string) *Host {
 	u, _ := url.Parse(hostURL)

oauth_device.go

@@ -29,9 +29,14 @@ func (oa *Flow) DeviceFlow() (*api.AccessToken, error) {
 	if stdout == nil {
 		stdout = os.Stdout
 	}
+
 	host := oa.Host
 	if host == nil {
-		host = GitHubHost("https://" + oa.Hostname)
+		host, err := NewGitHubHost("https://" + oa.Hostname)
+		if err != nil {
+			return nil, fmt.Errorf("error parsing the hostname '%s': %w", host, err)
+		}
+		oa.Host = host
 	}
 
 	code, err := device.RequestCode(httpClient, host.DeviceCodeURL, oa.ClientID, oa.Scopes)

oauth_webapp.go

@@ -14,8 +14,13 @@ import (
 // flow, blocks until the user completes authorization and is redirected back, and returns the access token.
 func (oa *Flow) WebAppFlow() (*api.AccessToken, error) {
 	host := oa.Host
+
 	if host == nil {
-		host = GitHubHost("https://" + oa.Hostname)
+		host, err := NewGitHubHost("https://" + oa.Hostname)
+		if err != nil {
+			return nil, fmt.Errorf("error parsing the hostname '%s': %w", host, err)
+		}
+		oa.Host = host
 	}
 
 	flow, err := webapp.InitFlow()