download https://go.googlecode.com/files/go1.1rc1.windows-amd64.zip,
and you will find a go/bin/go.exe~ file in it.
-rw-rw-rw- 2.0 unx 7591424 bl defN 1-May-13 14:08 go/bin/go.exe
-rw-rw-rw- 2.0 unx 9661952 bl defN 1-May-13 14:07 go/bin/go.exe~
i verified that bin/go~ is not present in go1.1rc1.linux-amd64.tar.gz.
i think it's a race detector version of go.exe, but why it's there in the windows/amd64
package, but not linux/amd64 tarball?