diff --git a/caches/leveldb.go b/caches/leveldb.go
index d1a177ad..f2f71d84 100644
--- a/caches/leveldb.go
+++ b/caches/leveldb.go
@@ -19,6 +19,7 @@ type LevelDBStore struct {
 
 var _ CacheStore = &LevelDBStore{}
 
+// NewLevelDBStore creates a leveldb store
 func NewLevelDBStore(dbfile string) (*LevelDBStore, error) {
 	db := &LevelDBStore{}
 	h, err := leveldb.OpenFile(dbfile, nil)
@@ -29,6 +30,7 @@ func NewLevelDBStore(dbfile string) (*LevelDBStore, error) {
 	return db, nil
 }
 
+// Put implements CacheStore
 func (s *LevelDBStore) Put(key string, value interface{}) error {
 	val, err := Encode(value)
 	if err != nil {
@@ -50,6 +52,7 @@ func (s *LevelDBStore) Put(key string, value interface{}) error {
 	return err
 }
 
+// Get implements CacheStore
 func (s *LevelDBStore) Get(key string) (interface{}, error) {
 	data, err := s.store.Get([]byte(key), nil)
 	if err != nil {
@@ -75,6 +78,7 @@ func (s *LevelDBStore) Get(key string) (interface{}, error) {
 	return s.v, err
 }
 
+// Del implements CacheStore
 func (s *LevelDBStore) Del(key string) error {
 	err := s.store.Delete([]byte(key), nil)
 	if err != nil {
@@ -89,6 +93,7 @@ func (s *LevelDBStore) Del(key string) error {
 	return err
 }
 
+// Close implements CacheStore
 func (s *LevelDBStore) Close() {
 	s.store.Close()
 }
diff --git a/caches/manager.go b/caches/manager.go
index 05045210..89a14106 100644
--- a/caches/manager.go
+++ b/caches/manager.go
@@ -6,6 +6,7 @@ package caches
 
 import "sync"
 
+// Manager represents a cache manager
 type Manager struct {
 	cacher             Cacher
 	disableGlobalCache bool
@@ -14,6 +15,7 @@ type Manager struct {
 	cacherLock sync.RWMutex
 }
 
+// NewManager creates a cache manager
 func NewManager() *Manager {
 	return &Manager{
 		cachers: make(map[string]Cacher),
@@ -27,12 +29,14 @@ func (mgr *Manager) SetDisableGlobalCache(disable bool) {
 	}
 }
 
+// SetCacher set cacher of table
 func (mgr *Manager) SetCacher(tableName string, cacher Cacher) {
 	mgr.cacherLock.Lock()
 	mgr.cachers[tableName] = cacher
 	mgr.cacherLock.Unlock()
 }
 
+// GetCacher returns a cache of a table
 func (mgr *Manager) GetCacher(tableName string) Cacher {
 	var cacher Cacher
 	var ok bool
diff --git a/contexts/hook.go b/contexts/hook.go
index 71ad8e87..70f114dd 100644
--- a/contexts/hook.go
+++ b/contexts/hook.go
@@ -31,6 +31,7 @@ func NewContextHook(ctx context.Context, sql string, args []interface{}) *Contex
 	}
 }
 
+// End finish the hook invokation
 func (c *ContextHook) End(ctx context.Context, result sql.Result, err error) {
 	c.Ctx = ctx
 	c.Result = result
@@ -38,19 +39,23 @@ func (c *ContextHook) End(ctx context.Context, result sql.Result, err error) {
 	c.ExecuteTime = time.Now().Sub(c.start)
 }
 
+// Hook represents a hook behaviour
 type Hook interface {
 	BeforeProcess(c *ContextHook) (context.Context, error)
 	AfterProcess(c *ContextHook) error
 }
 
+// Hooks implements Hook interface but contains multiple Hook
 type Hooks struct {
 	hooks []Hook
 }
 
+// AddHook adds a Hook
 func (h *Hooks) AddHook(hooks ...Hook) {
 	h.hooks = append(h.hooks, hooks...)
 }
 
+// BeforeProcess invoked before execute the process
 func (h *Hooks) BeforeProcess(c *ContextHook) (context.Context, error) {
 	ctx := c.Ctx
 	for _, h := range h.hooks {
@@ -63,6 +68,7 @@ func (h *Hooks) BeforeProcess(c *ContextHook) (context.Context, error) {
 	return ctx, nil
 }
 
+// AfterProcess invoked after exetue the process
 func (h *Hooks) AfterProcess(c *ContextHook) error {
 	firstErr := c.Err
 	for _, h := range h.hooks {
diff --git a/dialects/dialect.go b/dialects/dialect.go
index d9a640a4..b02ec4ae 100644
--- a/dialects/dialect.go
+++ b/dialects/dialect.go
@@ -79,32 +79,34 @@ type Base struct {
 	quoter  schemas.Quoter
 }
 
-func (b *Base) Quoter() schemas.Quoter {
-	return b.quoter
+// Quoter returns the current database Quoter
+func (db *Base) Quoter() schemas.Quoter {
+	return db.quoter
 }
 
-func (b *Base) Init(dialect Dialect, uri *URI) error {
-	b.dialect, b.uri = dialect, uri
+// Init initialize the dialect
+func (db *Base) Init(dialect Dialect, uri *URI) error {
+	db.dialect, db.uri = dialect, uri
 	return nil
 }
 
-func (b *Base) URI() *URI {
-	return b.uri
+// URI returns the uri of database
+func (db *Base) URI() *URI {
+	return db.uri
 }
 
-func (b *Base) DBType() schemas.DBType {
-	return b.uri.DBType
-}
-
-func (b *Base) FormatBytes(bs []byte) string {
+// FormatBytes formats bytes
+func (db *Base) FormatBytes(bs []byte) string {
 	return fmt.Sprintf("0x%x", bs)
 }
 
+// DropTableSQL returns drop table SQL
 func (db *Base) DropTableSQL(tableName string) (string, bool) {
 	quote := db.dialect.Quoter().Quote
 	return fmt.Sprintf("DROP TABLE IF EXISTS %s", quote(tableName)), true
 }
 
+// HasRecords returns true if the SQL has records returned
 func (db *Base) HasRecords(queryer core.Queryer, ctx context.Context, query string, args ...interface{}) (bool, error) {
 	rows, err := queryer.QueryContext(ctx, query, args...)
 	if err != nil {
@@ -118,6 +120,7 @@ func (db *Base) HasRecords(queryer core.Queryer, ctx context.Context, query stri
 	return false, nil
 }
 
+// IsColumnExist returns true if the column of the table exist
 func (db *Base) IsColumnExist(queryer core.Queryer, ctx context.Context, tableName, colName string) (bool, error) {
 	quote := db.dialect.Quoter().Quote
 	query := fmt.Sprintf(
@@ -132,11 +135,13 @@ func (db *Base) IsColumnExist(queryer core.Queryer, ctx context.Context, tableNa
 	return db.HasRecords(queryer, ctx, query, db.uri.DBName, tableName, colName)
 }
 
+// AddColumnSQL returns a SQL to add a column
 func (db *Base) AddColumnSQL(tableName string, col *schemas.Column) string {
 	s, _ := ColumnString(db.dialect, col, true)
 	return fmt.Sprintf("ALTER TABLE %v ADD %v", db.dialect.Quoter().Quote(tableName), s)
 }
 
+// CreateIndexSQL returns a SQL to create index
 func (db *Base) CreateIndexSQL(tableName string, index *schemas.Index) string {
 	quoter := db.dialect.Quoter()
 	var unique string
@@ -150,6 +155,7 @@ func (db *Base) CreateIndexSQL(tableName string, index *schemas.Index) string {
 		quoter.Join(index.Cols, ","))
 }
 
+// DropIndexSQL returns a SQL to drop index
 func (db *Base) DropIndexSQL(tableName string, index *schemas.Index) string {
 	quote := db.dialect.Quoter().Quote
 	var name string
@@ -161,16 +167,19 @@ func (db *Base) DropIndexSQL(tableName string, index *schemas.Index) string {
 	return fmt.Sprintf("DROP INDEX %v ON %s", quote(name), quote(tableName))
 }
 
+// ModifyColumnSQL returns a SQL to modify SQL
 func (db *Base) ModifyColumnSQL(tableName string, col *schemas.Column) string {
 	s, _ := ColumnString(db.dialect, col, false)
 	return fmt.Sprintf("ALTER TABLE %s MODIFY COLUMN %s", tableName, s)
 }
 
-func (b *Base) ForUpdateSQL(query string) string {
+// ForUpdateSQL returns for updateSQL
+func (db *Base) ForUpdateSQL(query string) string {
 	return query + " FOR UPDATE"
 }
 
-func (b *Base) SetParams(params map[string]string) {
+// SetParams set params
+func (db *Base) SetParams(params map[string]string) {
 }
 
 var (
diff --git a/engine.go b/engine.go
index ee98ed05..384928d6 100644
--- a/engine.go
+++ b/engine.go
@@ -1278,6 +1278,7 @@ func (engine *Engine) SetSchema(schema string) {
 	engine.dialect.URI().SetSchema(schema)
 }
 
+// AddHook adds a context Hook
 func (engine *Engine) AddHook(hook contexts.Hook) {
 	engine.db.AddHook(hook)
 }
@@ -1293,7 +1294,7 @@ func (engine *Engine) tbNameWithSchema(v string) string {
 	return dialects.TableNameWithSchema(engine.dialect, v)
 }
 
-// ContextHook creates a session with the context
+// Context creates a session with the context
 func (engine *Engine) Context(ctx context.Context) *Session {
 	session := engine.NewSession()
 	session.isAutoClose = true
diff --git a/engine_group.go b/engine_group.go
index 3e91cbd6..3569690b 100644
--- a/engine_group.go
+++ b/engine_group.go
@@ -79,7 +79,7 @@ func (eg *EngineGroup) Close() error {
 	return nil
 }
 
-// ContextHook returned a group session
+// Context returned a group session
 func (eg *EngineGroup) Context(ctx context.Context) *Session {
 	sess := eg.NewSession()
 	sess.isAutoClose = true
@@ -144,6 +144,7 @@ func (eg *EngineGroup) SetLogger(logger interface{}) {
 	}
 }
 
+// AddHook adds Hook
 func (eg *EngineGroup) AddHook(hook contexts.Hook) {
 	eg.Engine.AddHook(hook)
 	for i := 0; i < len(eg.slaves); i++ {
diff --git a/integrations/engine_test.go b/integrations/engine_test.go
index 1e2e9f4a..3b843f16 100644
--- a/integrations/engine_test.go
+++ b/integrations/engine_test.go
@@ -190,7 +190,7 @@ func TestSetSchema(t *testing.T) {
 
 func TestImport(t *testing.T) {
 	if testEngine.Dialect().URI().DBType != schemas.MYSQL {
-		t.SkipNow()
+		t.Skip()
 		return
 	}
 	sess := testEngine.NewSession()
diff --git a/integrations/tests.go b/integrations/tests.go
index 840b1020..512f3962 100644
--- a/integrations/tests.go
+++ b/integrations/tests.go
@@ -8,6 +8,7 @@ import (
 	"database/sql"
 	"flag"
 	"fmt"
+	"net/url"
 	"os"
 	"strings"
 	"testing"
@@ -97,6 +98,13 @@ func createEngine(dbType, connStr string) error {
 					return fmt.Errorf("db.Exec: %v", err)
 				}
 				db.Close()
+			case schemas.SQLITE, "sqlite":
+				u, err := url.Parse(connStr)
+				if err != nil {
+					return err
+				}
+				connStr = u.Path
+				*ignoreSelectUpdate = true
 			default:
 				*ignoreSelectUpdate = true
 			}
@@ -164,10 +172,12 @@ func createEngine(dbType, connStr string) error {
 	return nil
 }
 
+// PrepareEngine prepare tests ORM engine
 func PrepareEngine() error {
 	return createEngine(dbType, connString)
 }
 
+// MainTest the tests entrance
 func MainTest(m *testing.M) {
 	flag.Parse()
 
diff --git a/internal/json/json.go b/internal/json/json.go
index c9a2eb4e..ef52f51f 100644
--- a/internal/json/json.go
+++ b/internal/json/json.go
@@ -6,15 +6,15 @@ package json
 
 import "encoding/json"
 
-// JSONInterface represents an interface to handle json data
-type JSONInterface interface {
+// Interface represents an interface to handle json data
+type Interface interface {
 	Marshal(v interface{}) ([]byte, error)
 	Unmarshal(data []byte, v interface{}) error
 }
 
 var (
 	// DefaultJSONHandler default json handler
-	DefaultJSONHandler JSONInterface = StdJSON{}
+	DefaultJSONHandler Interface = StdJSON{}
 )
 
 // StdJSON implements JSONInterface via encoding/json
diff --git a/internal/utils/name.go b/internal/utils/name.go
index f5fc3ff7..840dd9e8 100644
--- a/internal/utils/name.go
+++ b/internal/utils/name.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 )
 
+// IndexName returns index name
 func IndexName(tableName, idxName string) string {
 	return fmt.Sprintf("IDX_%v_%v", tableName, idxName)
 }
diff --git a/internal/utils/reflect.go b/internal/utils/reflect.go
index 3dad6bfe..7973d4d3 100644
--- a/internal/utils/reflect.go
+++ b/internal/utils/reflect.go
@@ -8,6 +8,7 @@ import (
 	"reflect"
 )
 
+// ReflectValue returns value of a bean
 func ReflectValue(bean interface{}) reflect.Value {
 	return reflect.Indirect(reflect.ValueOf(bean))
 }
diff --git a/internal/utils/sql.go b/internal/utils/sql.go
index 5e68c4a4..369ca2b8 100644
--- a/internal/utils/sql.go
+++ b/internal/utils/sql.go
@@ -8,6 +8,7 @@ import (
 	"strings"
 )
 
+// IsSubQuery returns true if it contains a sub query
 func IsSubQuery(tbName string) bool {
 	const selStr = "select"
 	if len(tbName) <= len(selStr)+1 {
diff --git a/internal/utils/strings.go b/internal/utils/strings.go
index 72466705..86469c0f 100644
--- a/internal/utils/strings.go
+++ b/internal/utils/strings.go
@@ -8,10 +8,12 @@ import (
 	"strings"
 )
 
+// IndexNoCase index a string in a string with no care of capitalize
 func IndexNoCase(s, sep string) int {
 	return strings.Index(strings.ToLower(s), strings.ToLower(sep))
 }
 
+// SplitNoCase split a string by a seperator with no care of capitalize
 func SplitNoCase(s, sep string) []string {
 	idx := IndexNoCase(s, sep)
 	if idx < 0 {
@@ -20,6 +22,7 @@ func SplitNoCase(s, sep string) []string {
 	return strings.Split(s, s[idx:idx+len(sep)])
 }
 
+// SplitNNoCase split n by a seperator with no care of capitalize
 func SplitNNoCase(s, sep string, n int) []string {
 	idx := IndexNoCase(s, sep)
 	if idx < 0 {
diff --git a/internal/utils/zero.go b/internal/utils/zero.go
index 8f033c60..007e3c33 100644
--- a/internal/utils/zero.go
+++ b/internal/utils/zero.go
@@ -9,6 +9,7 @@ import (
 	"time"
 )
 
+// Zeroable represents an interface which could know if it's a zero value
 type Zeroable interface {
 	IsZero() bool
 }
@@ -21,39 +22,39 @@ func IsZero(k interface{}) bool {
 		return true
 	}
 
-	switch k.(type) {
+	switch t := k.(type) {
 	case int:
-		return k.(int) == 0
+		return t == 0
 	case int8:
-		return k.(int8) == 0
+		return t == 0
 	case int16:
-		return k.(int16) == 0
+		return t == 0
 	case int32:
-		return k.(int32) == 0
+		return t == 0
 	case int64:
-		return k.(int64) == 0
+		return t == 0
 	case uint:
-		return k.(uint) == 0
+		return t == 0
 	case uint8:
-		return k.(uint8) == 0
+		return t == 0
 	case uint16:
-		return k.(uint16) == 0
+		return t == 0
 	case uint32:
-		return k.(uint32) == 0
+		return t == 0
 	case uint64:
-		return k.(uint64) == 0
+		return t == 0
 	case float32:
-		return k.(float32) == 0
+		return t == 0
 	case float64:
-		return k.(float64) == 0
+		return t == 0
 	case bool:
-		return k.(bool) == false
+		return !t
 	case string:
-		return k.(string) == ""
+		return t == ""
 	case *time.Time:
-		return k.(*time.Time) == nilTime || IsTimeZero(*k.(*time.Time))
+		return t == nilTime || IsTimeZero(*t)
 	case time.Time:
-		return IsTimeZero(k.(time.Time))
+		return IsTimeZero(t)
 	case Zeroable:
 		return k.(Zeroable) == nil || k.(Zeroable).IsZero()
 	case reflect.Value: // for go version less than 1.13 because reflect.Value has no method IsZero
@@ -65,6 +66,7 @@ func IsZero(k interface{}) bool {
 
 var zeroType = reflect.TypeOf((*Zeroable)(nil)).Elem()
 
+// IsValueZero returns true if the reflect Value is a zero
 func IsValueZero(v reflect.Value) bool {
 	switch v.Kind() {
 	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Slice:
@@ -88,6 +90,7 @@ func IsValueZero(v reflect.Value) bool {
 	return false
 }
 
+// IsStructZero returns true if the Value is a struct and all fields is zero
 func IsStructZero(v reflect.Value) bool {
 	if !v.IsValid() || v.NumField() == 0 {
 		return true
@@ -120,6 +123,7 @@ func IsStructZero(v reflect.Value) bool {
 	return true
 }
 
+// IsArrayZero returns true is a slice of array is zero
 func IsArrayZero(v reflect.Value) bool {
 	if !v.IsValid() || v.Len() == 0 {
 		return true
@@ -134,11 +138,13 @@ func IsArrayZero(v reflect.Value) bool {
 	return true
 }
 
+// represents all zero times
 const (
 	ZeroTime0 = "0000-00-00 00:00:00"
 	ZeroTime1 = "0001-01-01 00:00:00"
 )
 
+// IsTimeZero return true if a time is zero
 func IsTimeZero(t time.Time) bool {
 	return t.IsZero() || t.Format("2006-01-02 15:04:05") == ZeroTime0 ||
 		t.Format("2006-01-02 15:04:05") == ZeroTime1
diff --git a/migrate/migrate.go b/migrate/migrate.go
index 82c58f90..19b4afe0 100644
--- a/migrate/migrate.go
+++ b/migrate/migrate.go
@@ -110,10 +110,7 @@ func (m *Migrate) RollbackLast() error {
 		return err
 	}
 
-	if err := m.RollbackMigration(lastRunnedMigration); err != nil {
-		return err
-	}
-	return nil
+	return m.RollbackMigration(lastRunnedMigration)
 }
 
 func (m *Migrate) getLastRunnedMigration() (*Migration, error) {
diff --git a/migrate/migrate_test.go b/migrate/migrate_test.go
index 19554f7e..3d7aa189 100644
--- a/migrate/migrate_test.go
+++ b/migrate/migrate_test.go
@@ -106,10 +106,7 @@ func TestInitSchema(t *testing.T) {
 		if err := tx.Sync2(&Person{}); err != nil {
 			return err
 		}
-		if err := tx.Sync2(&Pet{}); err != nil {
-			return err
-		}
-		return nil
+		return tx.Sync2(&Pet{})
 	})
 
 	err = m.Migrate()
diff --git a/session.go b/session.go
index 17abd453..d5ccb6dc 100644
--- a/session.go
+++ b/session.go
@@ -169,6 +169,7 @@ func (session *Session) db() *core.DB {
 	return session.engine.db
 }
 
+// Engine returns session Engine
 func (session *Session) Engine() *Engine {
 	return session.engine
 }
@@ -895,7 +896,7 @@ func (session *Session) incrVersionFieldValue(fieldValue *reflect.Value) {
 	}
 }
 
-// ContextHook sets the context on this session
+// Context sets the context on this session
 func (session *Session) Context(ctx context.Context) *Session {
 	session.ctx = ctx
 	return session
diff --git a/session_get.go b/session_get.go
index 6e65ea2f..e303176d 100644
--- a/session_get.go
+++ b/session_get.go
@@ -17,6 +17,7 @@ import (
 )
 
 var (
+	// ErrObjectIsNil return error of object is nil
 	ErrObjectIsNil = errors.New("object should not be nil")
 )
 
diff --git a/session_tx.go b/session_tx.go
index 33ef72c6..8763784c 100644
--- a/session_tx.go
+++ b/session_tx.go
@@ -85,7 +85,7 @@ func (session *Session) Commit() error {
 	return nil
 }
 
-// if current session is in a transaction
+// IsInTx if current session is in a transaction
 func (session *Session) IsInTx() bool {
 	return !session.isAutoCommit
 }