add context for modules

hosts/hosts.go

@@ -1,10 +1,11 @@
 package hosts
 
 import (
+	"context"
 	"net"
 )
 
 // HostMapper is a mapping from hostname to IP.
 type HostMapper interface {
-	Lookup(network, host string) ([]net.IP, bool)
+	Lookup(ctx context.Context, network, host string) ([]net.IP, bool)
 }