Copy pkg/signals verbatim from Serving. (#25)

signals/signal.go

@@ -0,0 +1,43 @@
+/*
+Copyright 2018 The Knative Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"os"
+	"os/signal"
+)
+
+var onlyOneSignalHandler = make(chan struct{})
+
+// SetupSignalHandler registered for SIGTERM and SIGINT. A stop channel is returned
+// which is closed on one of these signals. If a second signal is caught, the program
+// is terminated with exit code 1.
+func SetupSignalHandler() (stopCh <-chan struct{}) {
+	close(onlyOneSignalHandler) // panics when called twice
+
+	stop := make(chan struct{})
+	c := make(chan os.Signal, 2)
+	signal.Notify(c, shutdownSignals...)
+	go func() {
+		<-c
+		close(stop)
+		<-c
+		os.Exit(1) // second signal. Exit directly.
+	}()
+
+	return stop
+}

signals/signal_posix.go

@@ -0,0 +1,26 @@
+// +build !windows
+
+/*
+Copyright 2018 The Knative Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"os"
+	"syscall"
+)
+
+var shutdownSignals = []os.Signal{os.Interrupt, syscall.SIGTERM}

signals/signal_windows.go

@@ -0,0 +1,23 @@
+/*
+Copyright 2018 The Knative Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signals
+
+import (
+	"os"
+)
+
+var shutdownSignals = []os.Signal{os.Interrupt}