Update Dockerfile

Dockerfile

 FROM golang:1.10.3
 
 ENV DEBIAN_FRONTEND=noninteractive 
-RUN 	go get -u github.com/golang/dep/cmd/dep  github.com/ugorji/go/codec/codecgen  \
-		&& echo deb http://deb.debian.org/debian stretch-backports main > /etc/apt/sources.list.d/backports.list \
-                && apt-get update && apt-get install -y libgs-dev ghostscript wkhtmltopdf 
+RUN 	go get -u github.com/golang/dep/cmd/dep  github.com/ugorji/go/codec/codecgen
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