go.mod: bump wireguard-go version.

Fixes #219.

Signed-off-by: David Anderson <dave@natulte.net>

go.mod

@@ -20,7 +20,7 @@ require (
 	github.com/peterbourgon/ff/v2 v2.0.0
 	github.com/tailscale/hujson v0.0.0-20190930033718-5098e564d9b3 // indirect
 	github.com/tailscale/winipcfg-go v0.0.0-20200213045944-185b07f8233f
-	github.com/tailscale/wireguard-go v0.0.0-20200320054525-e913b7c8517d
+	github.com/tailscale/wireguard-go v0.0.0-20200325185614-bd634ffe2ded
 	golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6
 	golang.org/x/net v0.0.0-20200301022130-244492dfa37a // indirect
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d
@@ -31,3 +31,4 @@ require (
 	honnef.co/go/tools v0.0.1-2020.1.3 // indirect
 	rsc.io/goversion v1.2.0
 )
+