process: also handle SIGHUP in onInterruptSignal

`onInterruptSignal` is a function that accepts a cleanup function and
runs it on SIGINT and SIGTERM. Update to also run cleanup on SIGHUP.
Major use case is to handle broken SSH connections.

process.go

@@ -6,10 +6,11 @@ import (
 	"syscall"
 )
 
-// OnInterruptSignal invokes fn when SIGNINT/SIGTERM is received.
+// OnInterruptSignal invokes fn when an interrupt signal is received.
+// We loosely define the interrupt signal as SIGINT, SIGTERM, and SIGHUP.
 func onInterruptSignal(fn func()) {
 	signalChan := make(chan os.Signal, 1)
-	signal.Notify(signalChan, syscall.SIGINT, syscall.SIGTERM)
+	signal.Notify(signalChan, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
 	go func() {
 		<-signalChan
 		fn()