Fixes Ngrok now needing glibc.

Dockerfile

@@ -1,6 +1,17 @@
-FROM alpine:3.8
+FROM alpine:3.9
 MAINTAINER Werner Beroux <werner@beroux.com>
 
+RUN set -x && \
+    apk add --no-cache -t .deps ca-certificates && \
+    # Install glibc on Alpine (required by docker-compose) from
+    # https://github.com/sgerrand/alpine-pkg-glibc
+    # See also https://github.com/gliderlabs/docker-alpine/issues/11
+    wget -q -O /etc/apk/keys/sgerrand.rsa.pub https://alpine-pkgs.sgerrand.com/sgerrand.rsa.pub && \
+    wget https://github.com/sgerrand/alpine-pkg-glibc/releases/download/2.29-r0/glibc-2.29-r0.apk && \
+    apk add glibc-2.29-r0.apk && \
+    rm glibc-2.29-r0.apk && \
+    apk del --purge .deps
+
 RUN set -x \
     # Install ngrok (latest official stable from https://ngrok.com/download).
  && apk add --no-cache curl \
@@ -9,6 +20,7 @@ RUN set -x \
  && rm -f /ngrok.zip \
     # Create non-root user.
  && adduser -h /home/ngrok -D -u 6737 ngrok
+RUN  ngrok --version
 
 # Add config script.
 COPY --chown=ngrok ngrok.yml /home/ngrok/.ngrok2/