Update Dockerfile

Author: tannevaled

Dockerfile

@@ -12,9 +12,8 @@ RUN mkdir -p /packer/bin && \
     cd /packer/bin && \
     wget https://releases.hashicorp.com/packer/1.4.0/packer_1.4.0_linux_amd64.zip && \
     unzip packer_1.4.0_linux_amd64.zip
-RUN go get github.com/tcnksm/ghr && \
-    ls -alFhR && \
-    which ghr
+RUN go get -u github.com/tcnksm/ghr
+RUN which ghr
 RUN go get github.com/rackspace/gophercloud
 
 # FROM alpine:edge