fix panic when customfields map wasn't init

config.go

@@ -15,7 +15,7 @@ import (
 )
 
 func getConfig() *types.Configuration {
-	c := &types.Configuration{Customfields: make(map[string]interface{})}
+	c := &types.Configuration{Customfields: make(map[string]string)}
 
 	configFile := kingpin.Flag("config-file", "config file").Short('c').ExistingFile()
 	kingpin.Parse()

handlers.go

@@ -2,10 +2,11 @@ package main
 
 import (
 	"bytes"
+	"strconv"
 	"encoding/json"
 	"log"
 	"net/http"
-	"strconv"
+	// "strconv"
 	"strings"
 	"time"
 
@@ -48,6 +49,9 @@ func mainHandler(w http.ResponseWriter, r *http.Request) {
 
 	// falcopayload.OutputFields = make(map[string]interface{})
 	if len(config.Customfields) > 0 {
+		if falcopayload.OutputFields == nil {
+			falcopayload.OutputFields = make(map[string]interface{})
+		}
 		for key, value := range config.Customfields {
 			falcopayload.OutputFields[key] = value
 		}

types/types.go

@@ -22,7 +22,7 @@ type Configuration struct {
 	Alertmanager  alertmanagerOutputConfig
 	Elasticsearch elasticsearchOutputConfig
 	Influxdb      InfluxdbOutputConfig
-	Customfields  map[string]interface{}
+	Customfields  map[string]string
 }
 
 type slackOutputConfig struct {