Use the official Go source, follow redirects

dockerfiles/images/gogits/Dockerfile

@@ -13,7 +13,7 @@ ENV GOPATH /go
 RUN apt-get update && apt-get install --yes --force-yes curl git mercurial zip wget ca-certificates build-essential
 RUN apt-get install -yq vim sudo
 
-RUN curl -s http://docker.u.qiniudn.com/go1.2.1.src.tar.gz | tar -v -C /usr/local -xz
+RUN curl -sL https://golang.org/dl/go1.3.linux-amd64.tar.gz | tar -v -C /usr/local -xz
 RUN cd /usr/local/go/src && ./make.bash --no-clean 2>&1
 
 RUN go get -u -d github.com/gogits/gogs