TUN-8158: Bring back commit e653741885 and fixes infinite loop on linux when the socket is closed

vendor/github.com/fortytw2/leaktest/README.md

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+## Leaktest [![Build Status](https://travis-ci.org/fortytw2/leaktest.svg?branch=master)](https://travis-ci.org/fortytw2/leaktest) [![codecov](https://codecov.io/gh/fortytw2/leaktest/branch/master/graph/badge.svg)](https://codecov.io/gh/fortytw2/leaktest) [![Sourcegraph](https://sourcegraph.com/github.com/fortytw2/leaktest/-/badge.svg)](https://sourcegraph.com/github.com/fortytw2/leaktest?badge) [![Documentation](https://godoc.org/github.com/fortytw2/gpt?status.svg)](http://godoc.org/github.com/fortytw2/leaktest)
+
+Refactored, tested variant of the goroutine leak detector found in both
+`net/http` tests and the `cockroachdb` source tree.
+
+Takes a snapshot of running goroutines at the start of a test, and at the end -
+compares the two and _voila_. Ignores runtime/sys goroutines. Doesn't play nice
+with `t.Parallel()` right now, but there are plans to do so.
+
+### Installation
+
+Go 1.7+
+
+```
+go get -u github.com/fortytw2/leaktest
+```
+
+Go 1.5/1.6 need to use the tag `v1.0.0`, as newer versions depend on
+`context.Context`.
+
+### Example
+
+These tests fail, because they leak a goroutine
+
+```go
+// Default "Check" will poll for 5 seconds to check that all
+// goroutines are cleaned up
+func TestPool(t *testing.T) {
+    defer leaktest.Check(t)()
+
+    go func() {
+        for {
+            time.Sleep(time.Second)
+        }
+    }()
+}
+
+// Helper function to timeout after X duration
+func TestPoolTimeout(t *testing.T) {
+    defer leaktest.CheckTimeout(t, time.Second)()
+
+    go func() {
+        for {
+            time.Sleep(time.Second)
+        }
+    }()
+}
+
+// Use Go 1.7+ context.Context for cancellation
+func TestPoolContext(t *testing.T) {
+    ctx, _ := context.WithTimeout(context.Background(), time.Second)
+    defer leaktest.CheckContext(ctx, t)()
+
+    go func() {
+        for {
+            time.Sleep(time.Second)
+        }
+    }()
+}
+```
+
+## LICENSE
+
+Same BSD-style as Go, see LICENSE