From c8514ad7b7329f348a3a9a9d9490a99f59847a9e Mon Sep 17 00:00:00 2001
From: Matthew Holt <mholt@users.noreply.github.com>
Date: Mon, 6 Mar 2017 19:20:13 -0700
Subject: [PATCH] Avoid panic if reloading before server is started

See: https://forum.caddyserver.com/t/reloading-template-files-as-they-change/1483/3?u=matt

The server takes a moment to start; if USR1 is received before the
instance is saved, it would panic because no instances have been saved.
Instead, we just ignore the signal since no config has finished loading.
---
 sigtrap_posix.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sigtrap_posix.go b/sigtrap_posix.go
index 9ee7bbba..e046bee9 100644
--- a/sigtrap_posix.go
+++ b/sigtrap_posix.go
@@ -49,8 +49,14 @@ func trapSignalsPosix() {
 
 				// Start with the existing Caddyfile
 				instancesMu.Lock()
+				if len(instances) == 0 {
+					instancesMu.Unlock()
+					log.Println("[ERROR] SIGUSR1: No server instances are fully running")
+					continue
+				}
 				inst := instances[0] // we only support one instance at this time
 				instancesMu.Unlock()
+
 				updatedCaddyfile := inst.caddyfileInput
 				if updatedCaddyfile == nil {
 					// Hmm, did spawing process forget to close stdin? Anyhow, this is unusual.