From 38b74d1999280bc0a26e35fa94df90ce344d45f4 Mon Sep 17 00:00:00 2001
From: Adin Schmahmann <adin.schmahmann@gmail.com>
Date: Tue, 25 Aug 2020 10:07:30 -0400
Subject: [PATCH 1/2] feat: use deferred initialization of the asnStore

---
 asn.go | 38 ++++++++++++++++++++++++++++++++------
 1 file changed, 32 insertions(+), 6 deletions(-)

diff --git a/asn.go b/asn.go
index dd01ece..9ed8412 100644
--- a/asn.go
+++ b/asn.go
@@ -8,14 +8,10 @@ import (
 	"github.com/libp2p/go-cidranger"
 )
 
-var Store *asnStore
+var Store *indirectAsnStore
 
 func init() {
-	s, err := NewAsnStore()
-	if err != nil {
-		panic(err)
-	}
-	Store = s
+	Store = &indirectAsnStore{}
 }
 
 type networkWithAsn struct {
@@ -56,6 +52,17 @@ func (a *asnStore) AsnForIPv6(ip net.IP) (string, error) {
 // NewAsnStore returns a `asnStore` that can be queried for the Autonomous System Numbers
 // for a given IP address or a multiaddress which contains an IP address.
 func NewAsnStore() (*asnStore, error) {
+	if Store.store == nil {
+		store, err := newAsnStore()
+		if err != nil {
+			return nil, err
+		}
+		Store.store = store
+	}
+	return Store.store, nil
+}
+
+func newAsnStore() (*asnStore, error) {
 	cr := cidranger.NewPCTrieRanger()
 
 	for k, v := range ipv6CidrToAsnMap {
@@ -71,3 +78,22 @@ func NewAsnStore() (*asnStore, error) {
 
 	return &asnStore{cr}, nil
 }
+
+type indirectAsnStore struct {
+	store *asnStore
+}
+
+// AsnForIPv6 returns the AS number for the given IPv6 address.
+// If no mapping exists for the given IP, this function will
+// return an empty ASN and a nil error.
+func (a *indirectAsnStore) AsnForIPv6(ip net.IP) (string, error) {
+	if a.store == nil {
+		store, err := newAsnStore()
+		if err != nil {
+			panic(err)
+		}
+		a.store = store
+	}
+
+	return a.store.AsnForIPv6(ip)
+}

From d8ddb2ebb4e46f7360fcf1887a9d60eefdf608ef Mon Sep 17 00:00:00 2001
From: Adin Schmahmann <adin.schmahmann@gmail.com>
Date: Tue, 25 Aug 2020 11:23:16 -0400
Subject: [PATCH 2/2] feat: use background goroutine for indirectAsnStore
 initialization

---
 asn.go | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/asn.go b/asn.go
index 9ed8412..86be800 100644
--- a/asn.go
+++ b/asn.go
@@ -11,7 +11,7 @@ import (
 var Store *indirectAsnStore
 
 func init() {
-	Store = &indirectAsnStore{}
+	Store = newIndirectAsnStore()
 }
 
 type networkWithAsn struct {
@@ -49,19 +49,6 @@ func (a *asnStore) AsnForIPv6(ip net.IP) (string, error) {
 	return n.asn, nil
 }
 
-// NewAsnStore returns a `asnStore` that can be queried for the Autonomous System Numbers
-// for a given IP address or a multiaddress which contains an IP address.
-func NewAsnStore() (*asnStore, error) {
-	if Store.store == nil {
-		store, err := newAsnStore()
-		if err != nil {
-			return nil, err
-		}
-		Store.store = store
-	}
-	return Store.store, nil
-}
-
 func newAsnStore() (*asnStore, error) {
 	cr := cidranger.NewPCTrieRanger()
 
@@ -81,19 +68,30 @@ func newAsnStore() (*asnStore, error) {
 
 type indirectAsnStore struct {
 	store *asnStore
+	doneLoading chan struct{}
 }
 
 // AsnForIPv6 returns the AS number for the given IPv6 address.
 // If no mapping exists for the given IP, this function will
 // return an empty ASN and a nil error.
 func (a *indirectAsnStore) AsnForIPv6(ip net.IP) (string, error) {
-	if a.store == nil {
+	<-a.doneLoading
+	return a.store.AsnForIPv6(ip)
+}
+
+func newIndirectAsnStore() *indirectAsnStore {
+	a := &indirectAsnStore{
+		doneLoading: make(chan struct{}),
+	}
+
+	go func() {
+		defer close(a.doneLoading)
 		store, err := newAsnStore()
 		if err != nil {
 			panic(err)
 		}
 		a.store = store
-	}
+	}()
 
-	return a.store.AsnForIPv6(ip)
+	return a
 }