add GPG_KEY_DOWNLOAD_URL env

This allows user to choose where to download the gpg key from, original
source (default) or a trusted mirror site.

Signed-off-by: Tiankai Ma <[email protected]>

Author: tiankaima

install.sh

@@ -98,6 +98,10 @@ if [ -z "$DOWNLOAD_URL" ]; then
 	DOWNLOAD_URL=$DEFAULT_DOWNLOAD_URL
 fi
 
+if [ -z "GPG_KEY_DOWNLOAD_URL" ]; then
+	GPG_KEY_DOWNLOAD_URL=$DOWNLOAD_URL
+fi
+
 DEFAULT_REPO_FILE="docker-ce.repo"
 if [ -z "$REPO_FILE" ]; then
 	REPO_FILE="$DEFAULT_REPO_FILE"
@@ -501,7 +505,7 @@ do_install() {
 				$sh_c 'apt-get -qq update >/dev/null'
 				$sh_c "DEBIAN_FRONTEND=noninteractive apt-get -y -qq install $pre_reqs >/dev/null"
 				$sh_c 'install -m 0755 -d /etc/apt/keyrings'
-				$sh_c "curl -fsSL \"$DOWNLOAD_URL/linux/$lsb_dist/gpg\" -o /etc/apt/keyrings/docker.asc"
+				$sh_c "curl -fsSL \"GPG_KEY_DOWNLOAD_URL/linux/$lsb_dist/gpg\" -o /etc/apt/keyrings/docker.asc"
 				$sh_c "chmod a+r /etc/apt/keyrings/docker.asc"
 				$sh_c "echo \"$apt_repo\" > /etc/apt/sources.list.d/docker.list"
 				$sh_c 'apt-get -qq update >/dev/null'