Merge pull request #3 from teohhanhui/patch-1

Test the specified POSTGRES_DB

postgres/docker-healthcheck

@@ -3,12 +3,14 @@ set -eo pipefail
 
 host="$(hostname --ip-address || echo '127.0.0.1')"
 user="${POSTGRES_USER:-postgres}"
+db="${POSTGRES_DB:-$POSTGRES_USER}"
 export PGPASSWORD="${POSTGRES_PASSWORD:-}"
 
 args=(
 	# force postgres to not use the local unix socket (test "external" connectibility)
 	--host "$host"
 	--username "$user"
+	--dbname "$db"
 	--quiet --no-align --tuples-only
 )