diff --git a/alfred.go b/alfred.go
index 476ca53..c55159d 100644
--- a/alfred.go
+++ b/alfred.go
@@ -2,7 +2,7 @@
 * @Author: Bartuccio Antoine
 * @Date:   2018-07-23 15:24:22
 * @Last Modified by:   Bartuccio Antoine
-* @Last Modified time: 2019-01-04 10:52:37
+* @Last Modified time: 2019-01-05 17:47:10
  */
 
 package main
@@ -19,6 +19,7 @@ import (
 )
 
 func main() {
+
 	registeredCommands := map[string]func(*tb.Message){
 		tb.OnText:            commands.OnText,
 		"/registerprivate":   commands.RegisterPrivate,
diff --git a/shared/chat.go b/shared/chat.go
index c5b29a1..5578e6b 100644
--- a/shared/chat.go
+++ b/shared/chat.go
@@ -2,13 +2,14 @@
 * @Author: Bartuccio Antoine
 * @Date:   2018-07-27 15:37:59
 * @Last Modified by:   Bartuccio Antoine
-* @Last Modified time: 2019-01-04 10:49:45
+* @Last Modified time: 2019-01-05 17:46:26
  */
 
 package shared
 
 import (
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"sync"
 )
@@ -25,23 +26,28 @@ type chatDataFile struct {
 }
 
 // ChatData manage access to stored data about a chat
-var ChatData chatData
+var ChatData *chatData
 var cdf chatDataFile
 
 // InitChatData is meant to store infos about a chat.
-func InitChatData(path string) {
-	cdf = chatDataFile{path: path}
-	ChatData = chatData{data: make(map[int64]map[string]interface{})}
+func InitChatData(chatDataFilePath string) {
+
+	cdf = chatDataFile{path: chatDataFilePath}
+	ChatData = &chatData{data: make(map[int64]map[string]interface{})}
+
 	ChatData.mutex.Lock()
 	defer ChatData.mutex.Unlock()
+
 	cdf.read()
 
 }
 
 // Set stores data about a chat
-func (c chatData) Set(chat int64, key string, data interface{}) {
+func (c *chatData) Set(chat int64, key string, data interface{}) {
+
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
+
 	if _, exists := c.data[chat]; !exists {
 		c.data[chat] = make(map[string]interface{})
 	}
@@ -50,9 +56,11 @@ func (c chatData) Set(chat int64, key string, data interface{}) {
 }
 
 // Get retrieves data about a chat
-func (c chatData) Get(chat int64, key string) (interface{}, bool) {
+func (c *chatData) Get(chat int64, key string) (interface{}, bool) {
+
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
+
 	m, exists := c.data[chat]
 	if !exists {
 		return nil, false
@@ -64,22 +72,35 @@ func (c chatData) Get(chat int64, key string) (interface{}, bool) {
 	return data, true
 }
 
-func (c chatDataFile) read() {
+func (c *chatDataFile) read() {
+
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
+
 	data, err := ioutil.ReadFile(c.path)
 	if err != nil {
 		// File doesn't exist, skip import
 		return
 	}
-	json.Unmarshal(data, &ChatData.data)
+	if err := json.Unmarshal(data, &ChatData.data); err != nil {
+		fmt.Printf("Error while unmarshaling chat data with path %s, error : %v\n", c.path, err)
+	}
 }
 
-func (c chatDataFile) write() {
+func (c *chatDataFile) write() {
+
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
+
 	ChatData.mutex.Lock()
 	defer ChatData.mutex.Unlock()
-	data, _ := json.Marshal(ChatData.data)
-	ioutil.WriteFile(c.path, data, 0770)
+
+	data, err := json.Marshal(ChatData.data)
+	if err != nil {
+		fmt.Printf("Error while marshaling chat data file with path %s, error : %v\n", c.path, err)
+		return
+	}
+	if err := ioutil.WriteFile(c.path, data, 0770); err != nil {
+		fmt.Printf("Error writing chat data file with path %s, error %v\n", c.path, err)
+	}
 }
diff --git a/shared/history.go b/shared/history.go
index 3be9c46..daa55b4 100644
--- a/shared/history.go
+++ b/shared/history.go
@@ -2,13 +2,14 @@
 * @Author: Bartuccio Antoine
 * @Date:   2018-07-24 01:27:11
 * @Last Modified by:   Bartuccio Antoine
-* @Last Modified time: 2019-01-04 10:51:32
+* @Last Modified time: 2019-01-05 17:45:18
  */
 
 package shared
 
 import (
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
 	"sync"
 )
@@ -25,32 +26,39 @@ type historyFile struct {
 }
 
 // History manages acces to chat history
-var History history
+var History *history
 var hf historyFile
 
 // InitHistory init a chit history of a given size
-func InitHistory(size int, history_file_path string) {
+func InitHistory(size int, historyFilePath string) {
+
 	hf = historyFile{}
-	hf.path = history_file_path
-	History = history{}
+	hf.path = historyFilePath
+	History = &history{}
+
 	History.mutex.Lock()
 	defer History.mutex.Unlock()
+
 	History.size = size
 	History.data = make(map[int64][]string)
 	hf.read()
 }
 
 // Size get the number of messages saved in the history
-func (h history) Size() int {
+func (h *history) Size() int {
+
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
+
 	return h.size
 }
 
 // Message get a selected message in a chat history
-func (h history) Message(chatID int64, n int) string {
+func (h *history) Message(chatID int64, n int) string {
+
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
+
 	array, exists := h.data[chatID]
 	if exists && n >= 0 && n < len(array) {
 		return array[n]
@@ -59,9 +67,11 @@ func (h history) Message(chatID int64, n int) string {
 }
 
 // AddMessage append a message to a given chat
-func (h history) AddMessage(chatID int64, m string) {
+func (h *history) AddMessage(chatID int64, m string) {
+
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
+
 	if _, exists := h.data[chatID]; !exists {
 		h.data[chatID] = make([]string, h.size, h.size)
 	}
@@ -69,9 +79,11 @@ func (h history) AddMessage(chatID int64, m string) {
 }
 
 // LastMessage get the last message of a given chat
-func (h history) LastMessage(chatID int64) string {
+func (h *history) LastMessage(chatID int64) string {
+
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
+
 	if _, exists := h.data[chatID]; exists {
 		return h.data[chatID][h.size-1]
 	}
@@ -79,9 +91,11 @@ func (h history) LastMessage(chatID int64) string {
 }
 
 // ChatHistory get a copy of a given chat history
-func (h history) ChatHistory(chatID int64) []string {
+func (h *history) ChatHistory(chatID int64) []string {
+
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
+
 	array, exists := h.data[chatID]
 	if exists {
 		c := make([]string, h.size, h.size)
@@ -93,7 +107,8 @@ func (h history) ChatHistory(chatID int64) []string {
 
 // Add a message at the end of a chat and move everithyng up
 // Assert that the slice exists and mutex already locked
-func (h history) append(chatID int64, m string) {
+func (h *history) append(chatID int64, m string) {
+
 	c := make([]string, h.size-1, h.size-1)
 	array, _ := h.data[chatID]
 	copy(c, array[1:])
@@ -104,22 +119,35 @@ func (h history) append(chatID int64, m string) {
 	go hf.write()
 }
 
-func (h historyFile) read() {
+func (h *historyFile) read() {
+
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
+
 	data, err := ioutil.ReadFile(h.path)
 	if err != nil {
 		// File doesn't exist, skip import
 		return
 	}
-	json.Unmarshal(data, &History.data)
+	if err := json.Unmarshal(data, &History.data); err != nil {
+		fmt.Printf("Error while unmarshaling user history with path %s, error : %v\n", h.path, err)
+	}
 }
 
-func (h historyFile) write() {
+func (h *historyFile) write() {
+
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
+
 	History.mutex.Lock()
 	defer History.mutex.Unlock()
-	data, _ := json.Marshal(History.data)
-	ioutil.WriteFile(h.path, data, 0770)
+
+	data, err := json.Marshal(History.data)
+	if err != nil {
+		fmt.Printf("Error while marshaling history file with path %s, error : %v\n", h.path, err)
+		return
+	}
+	if err := ioutil.WriteFile(h.path, data, 0770); err != nil {
+		fmt.Printf("Error writing history file with path %s, error %v\n", h.path, err)
+	}
 }
diff --git a/shared/users.go b/shared/users.go
index 118cd31..1b5449f 100644
--- a/shared/users.go
+++ b/shared/users.go
@@ -2,7 +2,7 @@
 * @Author: Bartuccio Antoine
 * @Date:   2018-07-24 14:41:03
 * @Last Modified by:   Bartuccio Antoine
-* @Last Modified time: 2019-01-04 10:52:13
+* @Last Modified time: 2019-01-05 17:45:59
  */
 
 package shared
@@ -27,24 +27,29 @@ type usersFile struct {
 }
 
 // Users shared user for commands
-var Users users
+var Users *users
 var uf usersFile
 
 // InitUsers inits the User info storage
-func InitUsers(users_file_path string) {
+func InitUsers(usersFilePath string) {
+
 	uf = usersFile{}
-	uf.path = users_file_path
-	Users = users{}
+	uf.path = usersFilePath
+	Users = &users{}
+
 	Users.mutex.Lock()
 	defer Users.mutex.Unlock()
+
 	Users.data = make(map[string]map[string]string)
 	uf.read()
 }
 
 // Get an info about a given user
-func (u users) Get(username string, key string) (string, bool) {
+func (u *users) Get(username string, key string) (string, bool) {
+
 	u.mutex.Lock()
 	defer u.mutex.Unlock()
+
 	user, exists := u.data[username]
 	if !exists {
 		return "", false
@@ -56,9 +61,11 @@ func (u users) Get(username string, key string) (string, bool) {
 }
 
 // Set add an info about a given user
-func (u users) Set(username string, key, data string) {
+func (u *users) Set(username string, key, data string) {
+
 	u.mutex.Lock()
 	defer u.mutex.Unlock()
+
 	if _, exists := u.data[username]; !exists {
 		u.data[username] = make(map[string]string)
 	}
@@ -67,9 +74,11 @@ func (u users) Set(username string, key, data string) {
 }
 
 // GetUsernames get all usernames stored in settings
-func (u users) GetUsernames() []string {
+func (u *users) GetUsernames() []string {
+
 	u.mutex.Lock()
 	defer u.mutex.Unlock()
+
 	var usernames []string
 	for username := range u.data {
 		usernames = append(usernames, username)
@@ -78,7 +87,8 @@ func (u users) GetUsernames() []string {
 }
 
 // GetUserChat retrieve the chat of the user if registered
-func (u users) GetUserChat(username string) (*tb.Chat, error) {
+func (u *users) GetUserChat(username string) (*tb.Chat, error) {
+
 	serializedChat, exists := u.Get(username, "private_chat")
 	if !exists {
 		return nil, fmt.Errorf("No private chat registered for %s", username)
@@ -93,7 +103,8 @@ func (u users) GetUserChat(username string) (*tb.Chat, error) {
 }
 
 // SetUserChat register a private chat for an user
-func (u users) SetUserChat(username string, chat *tb.Chat) {
+func (u *users) SetUserChat(username string, chat *tb.Chat) {
+
 	serializedChat, err := json.Marshal(chat)
 	if err != nil {
 		return
@@ -102,22 +113,35 @@ func (u users) SetUserChat(username string, chat *tb.Chat) {
 	u.Set(username, "private_chat", string(serializedChat))
 }
 
-func (u usersFile) read() {
+func (u *usersFile) read() {
+
 	u.mutex.Lock()
 	defer u.mutex.Unlock()
+
 	data, err := ioutil.ReadFile(u.path)
 	if err != nil {
 		// File doesn't exist, skip import
 		return
 	}
-	json.Unmarshal(data, &Users.data)
+	if err := json.Unmarshal(data, &Users.data); err != nil {
+		fmt.Printf("Error while unmarshaling user file with path %s, error : %v\n", u.path, err)
+	}
 }
 
-func (u usersFile) write() {
+func (u *usersFile) write() {
+
 	u.mutex.Lock()
 	defer u.mutex.Unlock()
+
 	Users.mutex.Lock()
 	defer Users.mutex.Unlock()
-	data, _ := json.Marshal(Users.data)
-	ioutil.WriteFile(u.path, data, 0770)
+
+	data, err := json.Marshal(Users.data)
+	if err != nil {
+		fmt.Printf("Error while marshaling user file with path %s, error : %v\n", u.path, err)
+		return
+	}
+	if err := ioutil.WriteFile(u.path, data, 0770); err != nil {
+		fmt.Printf("Error writing user file with path %s, error : %v\n", u.path, err)
+	}
 }