lock down the version of shadow to v0.1.11

The latest vesion v0.1.12 was just released On Jul 27, 2022,
and it is causing issue (see below) on the govet check,

```
govet_shadow' started at Sun Jul 31 23:23:27 PDT 2022
go get: upgraded golang.org/x/net v0.0.0-20211112202133-69e39bad7dc2 => v0.0.0-20220722155237-a158d28d115b
go get: upgraded golang.org/x/sys v0.0.0-20211019181941-9d821ace8654 => v0.0.0-20220722155257-8c9f86f7a55f
go get: upgraded golang.org/x/tools v0.0.0-20190524140312-2c0ae7006135 => v0.1.12
/root/go/pkg/mod/github.com/grpc-ecosystem/[email protected]/client_metrics.go:7:2: missing go.sum entry for module providing package golang.org/x/net/context (imported by go.etcd.io/etcd/etcdserver/etcdserverpb); to add:
	go get go.etcd.io/etcd/etcdserver/etcdserverpb
/root/go/pkg/mod/google.golang.org/[email protected]/internal/transport/controlbuf.go:28:2: missing go.sum entry for module providing package golang.org/x/net/http2 (imported by go.etcd.io/etcd/embed); to add:
	go get go.etcd.io/etcd/embed
/root/go/pkg/mod/google.golang.org/[email protected]/internal/transport/controlbuf.go:29:2: missing go.sum entry for module providing package golang.org/x/net/http2/hpack (imported by github.com/soheilhy/cmux); to add:
	go get github.com/soheilhy/[email protected]
/root/go/pkg/mod/google.golang.org/[email protected]/server.go:36:2: missing go.sum entry for module providing package golang.org/x/net/trace (imported by go.etcd.io/etcd/embed); to add:
	go get go.etcd.io/etcd/embed
```

It isn't good to always to use the latest version. Instead, we should
lock down the version, and v0.1.11 was confirmed to be working.

Signed-off-by: Benjamin Wang <[email protected]>

test

@@ -466,7 +466,7 @@ function govet_shadow_pass {
 	# shellcheck disable=SC2206
 	fmtpkgs=($fmtpkgs)
 	# Golang 1.12 onwards the experimental -shadow option is no longer available with go vet
-	go get golang.org/x/tools/go/analysis/passes/shadow/cmd/shadow
+	go get golang.org/x/tools/go/analysis/passes/shadow/cmd/shadow@v0.1.11
 	export PATH=${GOPATH}/bin:${PATH}
 	# shellcheck disable=SC2230
 	shadow_tool=$(which shadow)