Simplify signal handling code.

This does not require `//go:build`.

src/signal.go

···
+// See https://pkg.go.dev/os/signal#hdr-Windows for a description of what this module
+// will do on Windows (tl;dr nothing calls the reload handler, the interrupt handler works
+// more or less how you'd expect).
+
+package git_pages
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+func OnReload(handler func()) {
+	sighup := make(chan os.Signal, 1)
+	signal.Notify(sighup, syscall.SIGHUP)
+	go func() {
+		for {
+			<-sighup
+			handler()
+		}
+	}()
+}
+
+func WaitForInterrupt() {
+	sigint := make(chan os.Signal, 1)
+	signal.Notify(sigint, syscall.SIGINT, syscall.SIGTERM)
+	<-sigint
+	signal.Stop(sigint)
+}

src/signal_other.go

···
-//go:build !unix
-
-package git_pages
-
-func OnReload(handler func()) {
-	// not implemented
-}
-
-func WaitForInterrupt() {
-	for {
-		// Ctrl+C not supported
-	}
-}

src/signal_posix.go

···
-//go:build unix
-
-package git_pages
-
-import (
-	"os"
-	"os/signal"
-	"syscall"
-)
-
-func OnReload(handler func()) {
-	sighup := make(chan os.Signal, 1)
-	signal.Notify(sighup, syscall.SIGHUP)
-	go func() {
-		for {
-			<-sighup
-			handler()
-		}
-	}()
-}
-
-func WaitForInterrupt() {
-	sigint := make(chan os.Signal, 1)
-	signal.Notify(sigint, syscall.SIGINT)
-	<-sigint
-	signal.Stop(sigint)
-}