go.mod: update wireguard-go version

Signed-off-by: David Crawshaw <crawshaw@tailscale.com>

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 v0.0.0-20200301220325-351e6067e97c
+	github.com/tailscale/wireguard-go v0.0.0-20200304231028-d7c58f854950
 	golang.org/x/crypto v0.0.0-20200221231518-2aa609cf4a9d
 	golang.org/x/net v0.0.0-20200301022130-244492dfa37a // indirect
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d