add web api

pkg/resolver/resolver.go

@@ -2,9 +2,14 @@ package resolver
 
 import (
 	"context"
+	"errors"
 	"net"
 )
 
+var (
+	ErrInvalid = errors.New("resolver invalid")
+)
+
 type Resolver interface {
 	// Resolve returns a slice of the host's IPv4 and IPv6 addresses.
 	// The network should be 'ip', 'ip4' or 'ip6', default network is 'ip'.