update to latest nodejs 10 base image (#221)

diff --git a/Dockerfile b/Dockerfile
index f20e7a1..8d26e71 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -15,7 +15,7 @@
 # limitations under the License.
 #
 
-FROM node:10.16.3
+FROM node:10.19.0
 
 # only package.json
 ADD package.json /