runtime: platform-independent faketime support

This adds a platform-independent implementation of nacl's faketime
support. It can be enabled by setting the faketime build tag.

Updates #30439.

Change-Id: Iee097004d56d796e6d2bfdd303a092c067ade87e
Reviewed-on: https://go-review.googlesource.com/c/go/+/192740
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/runtime/testdata/testfaketime/faketime.go b/src/runtime/testdata/testfaketime/faketime.go
new file mode 100644
index 0000000000..1fb15ebb16
--- /dev/null
+++ b/src/runtime/testdata/testfaketime/faketime.go
@@ -0,0 +1,28 @@
+// Copyright 2019 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.
+
+// Test faketime support. This is its own test program because we have
+// to build it with custom build tags and hence want to minimize
+// dependencies.
+
+package main
+
+import (
+	"os"
+	"time"
+)
+
+func main() {
+	println("line 1")
+	// Stream switch, increments time
+	os.Stdout.WriteString("line 2\n")
+	os.Stdout.WriteString("line 3\n")
+	// Stream switch, increments time
+	os.Stderr.WriteString("line 4\n")
+	// Time jump
+	time.Sleep(1 * time.Second)
+	os.Stdout.WriteString("line 5\n")
+	// Print the current time.
+	os.Stdout.WriteString(time.Now().UTC().Format(time.RFC3339))
+}