unix/linux: update Dockerfile to Go 1.17rc2

Change-Id: Idc623480fd6a4a2c733fa2eec05091112421af2b
Reviewed-on: https://go-review.googlesource.com/c/sys/+/334530
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/linux/Dockerfile b/unix/linux/Dockerfile
index caa8ea1..c88ac80 100644
--- a/unix/linux/Dockerfile
+++ b/unix/linux/Dockerfile
@@ -21,9 +21,9 @@
 RUN git clone --branch release/2.33/master --depth 1 git://sourceware.org/git/glibc.git
 
 # Get Go
-ENV GOLANG_VERSION 1.17beta1
+ENV GOLANG_VERSION 1.17rc2
 ENV GOLANG_DOWNLOAD_URL https://golang.org/dl/go$GOLANG_VERSION.linux-amd64.tar.gz
-ENV GOLANG_DOWNLOAD_SHA256 a479681705b65971f9db079bfce53c4393bfa241d952eb09de88fb40677d3c4c
+ENV GOLANG_DOWNLOAD_SHA256 328235edc7c7d2a51d6c6cb4d7ff97e97357654ef9e1098b9a4603a9d278ad04
 
 RUN curl -fsSL "$GOLANG_DOWNLOAD_URL" -o golang.tar.gz \
     && echo "$GOLANG_DOWNLOAD_SHA256  golang.tar.gz" | sha256sum -c - \