fix "concurrent map read/write" panics

Fixes #737

Author: mumoshu

pkg/state/state.go

@@ -10,6 +10,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/roboll/helmfile/pkg/environment"
 	"github.com/roboll/helmfile/pkg/event"
@@ -58,6 +59,9 @@ type HelmState struct {
 	tempDir    func(string, string) (string, error)
 
 	runner helmexec.Runner
+
+	vals      map[string]interface{}
+	valsMutex sync.Mutex
 }
 
 // SubHelmfileSpec defines the subhelmfile path and options

pkg/state/state_exec_tmpl.go

@@ -8,6 +8,12 @@ import (
 )
 
 func (st *HelmState) Values() (map[string]interface{}, error) {
+	st.valsMutex.Lock()
+	defer st.valsMutex.Unlock()
+	if st.vals != nil {
+		return st.vals, nil
+	}
+
 	vals := map[string]interface{}{}
 
 	if err := mergo.Merge(&vals, st.Env.Defaults, mergo.WithOverride); err != nil {
@@ -22,6 +28,8 @@ func (st *HelmState) Values() (map[string]interface{}, error) {
 		return nil, err
 	}
 
+	st.vals = vals
+
 	return vals, nil
 }