feat: update bootstrap_dns_android (#966)

* update with non_specified network

* remove wrongs

* add alternative bootstrapDialer

* do test

* Update dns_bootstrap_android_test.go

* example of alternative dialer

* public method

* move const

* Update dns_bootstrap_android_test.go

* no duplicated

* Rename infra/conf/dns_bootstrap_android.go to transport/internet/system_dns_android.go

* Update system_dns_android.go

* Update and rename infra/conf/dns_bootstrap_android_test.go to transport/internet/system_dns_android_test.go

* no imports

* Update system_dns_android.go

* Update system_dns_android_test.go

* create systemDNS

* Create system_dns_android.go

* Update system_dialer.go

* call Resolver on systemDialer

* create system_dns_test.go

* resolver.LookupIP params

* param fix

* noneed TestSystemDNSResolver

* revert: no specified resolver

* Delete system_dns.go

* android only

* android only test

* typo

transport/internet/system_dns_android.go

@@ -0,0 +1,26 @@
+// +build android
+
+package internet
+
+import (
+	"context"
+	"net"
+)
+
+const SystemDNS = "8.8.8.8:53"
+
+type DNSResolverFunc func() *net.Resolver
+
+var NewDNSResolver DNSResolverFunc = func() *net.Resolver {
+	return &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, _ string) (net.Conn, error) {
+			var dialer net.Dialer
+			return dialer.DialContext(ctx, network, SystemDNS)
+		},
+	}
+}
+
+func init() {
+	net.DefaultResolver = NewDNSResolver()
+}

transport/internet/system_dns_android_test.go

@@ -0,0 +1,15 @@
+// +build android
+
+package internet
+
+import (
+	"context"
+	"testing"
+)
+
+func TestDNSResolver(t *testing.T) {
+	resolver := NewDNSResolver()
+	if ips, err := resolver.LookupIP(context.Background(), "ip", "www.google.com"); err != nil {
+		t.Errorf("failed to lookupIP, %v, %v", ips, err)
+	}
+}