fix session key

backend/util/common/random.go

@@ -1,13 +1,26 @@
 package common
 
-import "math/rand"
+import (
+	"math/rand"
+	"time"
+)
 
-var allSeq [62]rune
+var (
+	allSeq []rune
+	rnd    = rand.New(rand.NewSource(time.Now().UnixNano()))
+)
+
+func init() {
+	chars := "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
+	for _, char := range chars {
+		allSeq = append(allSeq, char)
+	}
+}
 
 func Random(n int) string {
 	runes := make([]rune, n)
 	for i := 0; i < n; i++ {
-		runes[i] = allSeq[rand.Intn(len(allSeq))]
+		runes[i] = allSeq[rnd.Intn(len(allSeq))]
 	}
 	return string(runes)
 }