Custom sql valuer that insert null to database if zero value is passed to it.

zeroisnull.go

// https://go.dev/play/p/gTzl_yht11I

package main

import (
	"database/sql/driver"
	"fmt"
)

type valuer[T comparable] struct {
	value *T
	zero  T
}

func (v *valuer[T]) Value() (driver.Value, error) {
	return v.value, nil
}

func ZeroIsNull[T comparable](src T) driver.Valuer {
	v := &valuer[T]{}
	v.value = &src
	if src == v.zero {
		v.value = (*T)(nil)
	}

	return v
}

func main() {
	v, _ := ZeroIsNull[string]("").Value()
	fmt.Printf("%#v\n", v)

	v, _ = ZeroIsNull[string]("test").Value()
	fmt.Printf("%#v\n", *v.(*string))

	v, _ = ZeroIsNull[uint64](uint64(0)).Value()
	fmt.Printf("%#v\n", v)

	v, _ = ZeroIsNull[uint64](uint64(42)).Value()
	fmt.Printf("%#v\n", *v.(*uint64))
}