hack/with-go-mod.sh: warn on stderr

Signed-off-by: Bjorn Neergaard <bjorn.neergaard@docker.com>

hack/with-go-mod.sh

@@ -14,8 +14,10 @@ ROOTDIR="$(git -C "$SCRIPTDIR" rev-parse --show-toplevel)"
 if test -e "${ROOTDIR}/go.mod"; then
 	{
 		scriptname=$(basename "$0")
-		echo "${scriptname}: WARN: go.mod exists in the repository root!"
-		echo "${scriptname}: WARN: Using your go.mod instead of our generated version -- this may misbehave!"
+		cat >&2 <<- EOF
+			$scriptname: WARN: go.mod exists in the repository root!
+			$scriptname: WARN: Using your go.mod instead of our generated version -- this may misbehave!
+		EOF
 	} >&2
 else
 	set -x