赋值角色时带上过期时间

agora.go

 	return SimpleTokenBuilder{CreateAccessToken(appID, appCertificate, channelName, uid)}
 }
 
-func (builder *SimpleTokenBuilder) InitPrivileges(role Role) {
+// InitPrivileges expireTimestamp 为0时长期有效
+func (builder *SimpleTokenBuilder) InitPrivileges(role Role, expireTimestamp uint32) {
 	rolepri := uint16(role)
 	for key, value := range RolePrivileges[rolepri] {
 		builder.Token.Message[key] = value