package models type Order struct { Id uint `gorm:"primaryKey"` Status string ProductTypeId uint ProductType ProductType ProductAmount uint Description string CustomerId uint `gorm:"null;foreignKey:CustomerId;"` // want "Null safety error in \"Order\" model, field \"CustomerId\": column nullable policy doesn't match to tag nullable policy" Customer Customer CreatedAt int64 `gorm:"autoCreateTime"` DeadlineDate int64 } type ProductType struct { Id uint `gorm:"primaryKey"` Name string } type Customer struct { Id uint `gorm:"primaryKey"` Title string Contact string Orders []Order `gorm:"foreignKey:CustomerId"` }