dl: add go1.18.6

Change-Id: I2ca85a5774d1bc611f06d7e60e5d94ba00c5225f
Reviewed-on: https://go-review.googlesource.com/c/dl/+/428696
Auto-Submit: Gopher Robot <gobot@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

go1.18.6/main.go

@@ -0,0 +1,24 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The go1.18.6 command runs the go command from Go 1.18.6.
+//
+// To install, run:
+//
+//	$ go install golang.org/dl/go1.18.6@latest
+//	$ go1.18.6 download
+//
+// And then use the go1.18.6 command as if it were your normal go
+// command.
+//
+// See the release notes at https://go.dev/doc/devel/release#go1.18.minor.
+//
+// File bugs at https://go.dev/issue/new.
+package main
+
+import "golang.org/dl/internal/version"
+
+func main() {
+	version.Run("go1.18.6")
+}