use go1.18 to build gitea (#19099)

* use go1.18 to build gitea& update min go version to 1.17

* bump in a few more places

* add a few simple tests for isipprivate

* update go.mod

* update URL to https://go.dev/dl/

* golangci-lint

* attempt golangci-lint workaround

* change version

* bump fumpt version

* skip strings.title test

* go mod tidy

* update tests as some aren't private??

* update tests

2 files changed, 57 insertions, 7 deletions

diff --git a/modules/util/net.go b/modules/util/net.go
index 54c0a2ca39..0339325dc3 100644
--- a/modules/util/net.go
+++ b/modules/util/net.go
@@ -8,12 +8,6 @@ import (
 	"net"
 )
 
-// IsIPPrivate for net.IP.IsPrivate. TODO: replace with `ip.IsPrivate()` if min go version is bumped to 1.17
 func IsIPPrivate(ip net.IP) bool {
-	if ip4 := ip.To4(); ip4 != nil {
-		return ip4[0] == 10 ||
-			(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
-			(ip4[0] == 192 && ip4[1] == 168)
-	}
-	return len(ip) == net.IPv6len && ip[0]&0xfe == 0xfc
+	return ip.IsPrivate()
 }
diff --git a/modules/util/net_test.go b/modules/util/net_test.go
new file mode 100644
index 0000000000..93a95ab123
--- /dev/null
+++ b/modules/util/net_test.go
@@ -0,0 +1,56 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsIPPPrivate(t *testing.T) {
+	cases := []struct {
+		ip        string
+		isPrivate bool
+	}{
+		// case 0
+		{
+			ip:        "127.0.0.1",
+			isPrivate: false, // TODO: according to go, this isn't private?
+		},
+		// case 1
+		{
+			ip:        "127.1.2.3",
+			isPrivate: false, // TODO: according to go, this isn't private?
+		},
+		// case 2
+		{
+			ip:        "10.255.255.0",
+			isPrivate: true,
+		},
+		// case 3
+		{
+			ip:        "8.8.8.8",
+			isPrivate: false,
+		},
+		// case 4
+		{
+			ip:        "::1",
+			isPrivate: false, // TODO: according to go, this isn't private?
+		},
+		// case 4
+		{
+			ip:        "2a12:7c40::f00d",
+			isPrivate: false,
+		},
+	}
+
+	for n, c := range cases {
+		i := net.ParseIP(c.ip)
+		p := IsIPPrivate(i)
+		assert.Equal(t, c.isPrivate, p, "case %d: should be equal", n)
+	}
+}