ui/progress: extract signal handling into own package

internal/ui/signals/signals.go

@@ -0,0 +1,24 @@
+package signals
+
+import (
+	"os"
+	"sync"
+)
+
+// GetProgressChannel returns a channel with which a single listener
+// receives each incoming signal.
+func GetProgressChannel() <-chan os.Signal {
+	signals.Once.Do(func() {
+		signals.ch = make(chan os.Signal, 1)
+		setupSignals()
+	})
+
+	return signals.ch
+}
+
+// XXX The fact that signals is a single global variable means that only one
+// listener receives each incoming signal.
+var signals struct {
+	ch chan os.Signal
+	sync.Once
+}

internal/ui/signals/signals_bsd.go

@@ -0,0 +1,12 @@
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package signals
+
+import (
+	"os/signal"
+	"syscall"
+)
+
+func setupSignals() {
+	signal.Notify(signals.ch, syscall.SIGINFO, syscall.SIGUSR1)
+}

internal/ui/signals/signals_sysv.go

@@ -0,0 +1,12 @@
+// +build aix linux solaris
+
+package signals
+
+import (
+	"os/signal"
+	"syscall"
+)
+
+func setupSignals() {
+	signal.Notify(signals.ch, syscall.SIGUSR1)
+}

internal/ui/signals/signals_windows.go

@@ -0,0 +1,3 @@
+package signals
+
+func setupSignals() {}