diff -Nru golang-1.21-1.21.1/debian/changelog golang-1.21-1.21.1/debian/changelog
--- golang-1.21-1.21.1/debian/changelog	2023-09-07 11:51:55.000000000 +0800
+++ golang-1.21-1.21.1/debian/changelog	2023-10-25 16:21:36.000000000 +0800
@@ -1,3 +1,13 @@
+golang-1.21 (1.21.1-1~20.04) focal; urgency=medium
+
+  * Backport to Focal (LP: #2040269)
+  * d/control{,.in}: downgrade debhelper compat level to 12
+  * Build with Go 1.18
+    + d/control{,.in}: use golang-1.18-go in Build-Depends
+    + d/rules: use /usr/lib/go-1.18/bin/go to set GOROOT_BOOTSTRAP path
+
+ -- Shengjing Zhu <shengjing.zhu@canonical.com>  Wed, 25 Oct 2023 16:21:36 +0800
+
 golang-1.21 (1.21.1-1) unstable; urgency=medium
 
   * Team upload
diff -Nru golang-1.21-1.21.1/debian/control golang-1.21-1.21.1/debian/control
--- golang-1.21-1.21.1/debian/control	2023-09-07 11:51:55.000000000 +0800
+++ golang-1.21-1.21.1/debian/control	2023-10-25 16:21:36.000000000 +0800
@@ -12,8 +12,8 @@
            Anthony Fok <foka@debian.org>
 Section: golang
 Priority: optional
-Build-Depends: debhelper-compat (= 13),
-               golang-any (>= 2:1.17~) | golang-go (>= 2:1.17~) | gccgo (>= 4:12~),
+Build-Depends: debhelper-compat (= 12),
+               golang-1.18-go,
                netbase
 Standards-Version: 4.6.2
 Vcs-Browser: https://salsa.debian.org/go-team/compiler/golang/tree/golang-1.21
diff -Nru golang-1.21-1.21.1/debian/control.in golang-1.21-1.21.1/debian/control.in
--- golang-1.21-1.21.1/debian/control.in	2023-09-07 11:51:55.000000000 +0800
+++ golang-1.21-1.21.1/debian/control.in	2023-10-25 16:21:36.000000000 +0800
@@ -8,8 +8,8 @@
            Anthony Fok <foka@debian.org>
 Section: golang
 Priority: optional
-Build-Depends: debhelper-compat (= 13),
-               golang-any (>= 2:1.17~) | golang-go (>= 2:1.17~) | gccgo (>= 4:12~),
+Build-Depends: debhelper-compat (= 12),
+               golang-1.18-go,
                netbase
 Standards-Version: 4.6.2
 Vcs-Browser: https://salsa.debian.org/go-team/compiler/golang/tree/golang-X.Y
diff -Nru golang-1.21-1.21.1/debian/rules golang-1.21-1.21.1/debian/rules
--- golang-1.21-1.21.1/debian/rules	2023-09-07 11:51:55.000000000 +0800
+++ golang-1.21-1.21.1/debian/rules	2023-10-25 16:21:36.000000000 +0800
@@ -102,7 +102,7 @@
 override_dh_auto_build-arch:
 	[ -f VERSION ] || echo "debian snapshot $(DEB_VERSION)" > VERSION
 
-	export GOROOT_BOOTSTRAP=$$(env -i GOPATH=$(GOPATH) go env GOROOT) \
+	export GOROOT_BOOTSTRAP=$$(env -i GOPATH=$(GOPATH) /usr/lib/go-1.18/bin/go env GOROOT) \
 	&& cd $(CURDIR)/src \
 	&& $(CURDIR)/debian/helpers/goenv.sh bash ./make.bash --no-banner