Use crosbymichael/golang as base image

Dockerfile

@@ -1,13 +1,5 @@
-FROM ubuntu:12.04
+FROM crosbymichael/golang
 
-RUN apt-get update
-
-RUN apt-get install -y curl                                                       
-RUN curl -s https://go.googlecode.com/files/go1.2.linux-amd64.tar.gz | tar -v -C /opt -xz ;\
-    cp -a /opt/go/* /usr/local/                                                             ;\
-    rm -rf /opt/go;
-
-ENV GOROOT /usr/local/
 ADD . /app/
 WORKDIR /app/
 RUN go build dockerui.go