[release-branch.go1.24] cmd/go: initialize req.Header when loading git credential

Fixes golang#71687

Change-Id: I3d733a50b4451dfb571aba91a28387ba9e0614dc
Reviewed-on: https://go-review.googlesource.com/c/go/+/647615
Reviewed-by: Michael Matloob <[email protected]>
Reviewed-by: Sam Thanawalla <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
(cherry picked from commit 58834c3)
Reviewed-on: https://go-review.googlesource.com/c/go/+/648936
Reviewed-by: Dmitri Shuralyov <[email protected]>
TryBot-Bypass: Dmitri Shuralyov <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>

Author: quantonganh

src/cmd/go/internal/auth/auth.go

@@ -128,7 +128,8 @@ func runGoAuth(client *http.Client, res *http.Response, url string) {
 	// If no GOAUTH command provided a credential for the given url
 	// and an error occurred, log the error.
 	if cfg.BuildX && url != "" {
-		if ok := loadCredential(&http.Request{}, url); !ok && len(cmdErrs) > 0 {
+		req := &http.Request{Header: make(http.Header)}
+		if ok := loadCredential(req, url); !ok && len(cmdErrs) > 0 {
 			log.Printf("GOAUTH encountered errors for %s:", url)
 			for _, err := range cmdErrs {
 				log.Printf("  %v", err)

src/cmd/go/testdata/script/goauth_git.txt

@@ -49,6 +49,8 @@ go get vcs-test.golang.org/auth/or401
 go mod tidy
 go list all
 stdout vcs-test.golang.org/auth/or404
+# With cached credentials, re-downloading in debug mode should succeed.
+go get -x vcs-test.golang.org/auth/or401
 
 # Clearing GOAUTH credentials should result in failures.
 env GOAUTH='off'