exp/cmd/issueserver: fix build

Change-Id: I21469ef0bab792993a6847063d86871f005a09fe
Reviewed-on: https://upspin-review.googlesource.com/10262
Reviewed-by: Andrew Gerrand <adg@golang.org>
diff --git a/cmd/issueserver/main.go b/cmd/issueserver/main.go
index aaf3962..5aa269b 100644
--- a/cmd/issueserver/main.go
+++ b/cmd/issueserver/main.go
@@ -109,7 +109,7 @@
 // $HOME/upspin/issueserver-github-token of the format "token".
 func getGithubToken() (string, error) {
 	file := filepath.Join(config.Home(), "upspin", "issueserver-github-token")
-	slurp, err := ioutil.ReadFile(file)
+	token, err := ioutil.ReadFile(file)
 	if err != nil {
 		return "", err
 	}