fix application bug

vendor/github.com/mholt/caddy/caddyhttp/proxy/policy.go

@@ -16,6 +16,7 @@ package proxy
 
 import (
 	"hash/fnv"
+	"log"
 	"math"
 	"math/rand"
 	"net"
@@ -139,7 +140,9 @@ func hostByHashing(pool HostPool, s string) *UpstreamHost {
 // hash calculates a hash based on string s
 func hash(s string) uint32 {
 	h := fnv.New32a()
-	h.Write([]byte(s))
+	if _, err := h.Write([]byte(s)); err != nil {
+		log.Println("[ERROR] failed to write bytes: ", err)
+	}
 	return h.Sum32()
 }