TableName return the table name of a given gorm model.
It checks whetehr the method TableName has been used
or not. It then retreives the appropriate table name.
This function accepts both, model and a its pointer
type Field struct {
Name string `gorm:"column:Field"`
Type string `gorm:"column:Type"`
Null string `gorm:"column:Null"`
Key string `gorm:"column:Key"`
Default *string `gorm:"column:Default"`
Extra string `gorm:"column:Extra"`
}