playground: update to 1.10.3

Change-Id: I0ecea2cf6ef5a3e42730db38b45540195050b310
Reviewed-on: https://go-review.googlesource.com/125303
Reviewed-by: Andrew Bonventre <andybons@golang.org>
diff --git a/Dockerfile b/Dockerfile
index cf91c40..41a0849 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -8,7 +8,7 @@
 ENV PATH /usr/local/go/bin:$GOPATH/bin:$PATH
 ENV GOROOT_BOOTSTRAP /usr/local/gobootstrap
 ENV CGO_ENABLED=0
-ENV GO_VERSION 1.10.2
+ENV GO_VERSION 1.10.3
 ENV BUILD_DEPS 'curl bzip2 git gcc patch libc6-dev ca-certificates'
 
 # Fake time