Use a context to ensure a time-based deadline for update operations.

src/fetch.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"io"
 
@@ -11,10 +12,10 @@ import (
 	"github.com/go-git/go-git/v6/storage/memory"
 )
 
-func FetchRepository(repoURL string, branch string) (*Manifest, error) {
+func FetchRepository(ctx context.Context, repoURL string, branch string) (*Manifest, error) {
 	storer := memory.NewStorage()
 
-	repo, err := git.Clone(storer, nil, &git.CloneOptions{
+	repo, err := git.CloneContext(ctx, storer, nil, &git.CloneOptions{
 		Bare:          true,
 		URL:           repoURL,
 		ReferenceName: plumbing.ReferenceName(branch),

src/pages.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"io"
@@ -176,7 +177,9 @@ func putPage(w http.ResponseWriter, r *http.Request) error {
 		branch = "pages"
 	}
 
-	result := UpdateWithTimeout(webRoot, repoURL, branch, updateTimeout)
+	ctx, cancel := context.WithTimeout(r.Context(), updateTimeout)
+	defer cancel()
+	result := Update(ctx, webRoot, repoURL, branch)
 	if result.manifest != nil {
 		w.Header().Add("Content-Location", r.URL.String())
 	}
@@ -285,7 +288,9 @@ func postPage(w http.ResponseWriter, r *http.Request) error {
 		return fmt.Errorf("invalid clone URL")
 	}
 
-	result := UpdateWithTimeout(webRoot, repoURL, "pages", updateTimeout)
+	ctx, cancel := context.WithTimeout(r.Context(), updateTimeout)
+	defer cancel()
+	result := Update(ctx, webRoot, repoURL, "pages")
 	switch result.outcome {
 	case UpdateError:
 		w.WriteHeader(http.StatusServiceUnavailable)

src/update.go

@@ -1,9 +1,10 @@
 package main
 
 import (
+	"context"
+	"errors"
 	"fmt"
 	"log"
-	"time"
 )
 
 type UpdateOutcome int
@@ -23,6 +24,7 @@ type UpdateResult struct {
 }
 
 func Update(
+	ctx context.Context,
 	webRoot string,
 	repoURL string,
 	branch string,
@@ -33,8 +35,11 @@ func Update(
 	log.Println("update:", webRoot, repoURL, branch)
 
 	outcome := UpdateError
-	fetchManifest, err = FetchRepository(repoURL, branch)
-	if err == nil {
+	fetchManifest, err = FetchRepository(ctx, repoURL, branch)
+	if errors.Is(err, context.DeadlineExceeded) {
+		outcome = UpdateTimeout
+		err = fmt.Errorf("update timeout")
+	} else if err == nil {
 		oldManifest, _ = backend.GetManifest(webRoot)
 		newManifest, err = StoreManifest(backend, webRoot, fetchManifest)
 		if err == nil {
@@ -65,22 +70,3 @@ func Update(
 
 	return UpdateResult{outcome, newManifest, err}
 }
-
-func UpdateWithTimeout(
-	webRoot string,
-	repoURL string,
-	branch string,
-	timeout time.Duration,
-) UpdateResult {
-	c := make(chan UpdateResult, 1)
-	go func() {
-		result := Update(webRoot, repoURL, branch)
-		c <- result
-	}()
-	select {
-	case result := <-c:
-		return result
-	case <-time.After(timeout):
-		return UpdateResult{outcome: UpdateTimeout, err: fmt.Errorf("update timeout")}
-	}
-}