Updated to use Ubuntu 18.04 and MongoDB 4.2

Author: sindbach

mongodb/Dockerfile

@@ -1,8 +1,10 @@
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
-RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 2930ADAE8CAF5059EE73BB4B58712A2291FA4AD5
+RUN apt-get update && apt-get install -y wget gnupg
 
-RUN echo "deb [ arch=amd64,arm64 ] http://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/3.6 multiverse" | tee /etc/apt/sources.list.d/mongodb-org-3.6.list
+RUN wget -qO - https://www.mongodb.org/static/pgp/server-4.2.asc | apt-key add -
+
+RUN echo "deb [ arch=amd64 ] http://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.2 multiverse" | tee /etc/apt/sources.list.d/mongodb-org-4.2.list
 
 RUN apt-get update && apt-get install -y mongodb-org && apt-get clean