Learn how to register and run seeders using runner.RunAll() and runner.Run() methods.

Running Seeders

Once you've defined your seeders, use the seeder runner to register and execute them.

Auto-Registration with `init()`

Similar to migrations, seeders can be auto-registered from init() functions using seeder.AutoRegister(). This is the recommended approach when using migrator.Run().

seeders/user_seeder.go

package seeders

import (
    "database/sql"

    "github.com/gopackx/go-migration/seeder"
)

func init() {
    seeder.AutoRegister("UserSeeder", &UserSeeder{})
}

type UserSeeder struct{}

func (s *UserSeeder) Run(db *sql.DB) error {
    _, err := db.Exec(
        "INSERT INTO users (name, email) VALUES ($1, $2)",
        "Alice", "alice@example.com",
    )
    return err
}

When using migrator.Run(), auto-registered seeders are discovered automatically — no manual registration needed. Just blank-import the seeders package in your main.go:

main.go

package main

import (
    "github.com/gopackx/go-migration/migrator"
    _ "your-project/migrations"
    _ "your-project/seeders" // triggers init() auto-registration
)

func main() {
    migrator.Run()
}

seeder.AutoRegister() panics on duplicate names, just like migrator.AutoRegister(). This ensures configuration mistakes are caught at startup.

Manual Registration

For more control, you can register seeders manually with the runner:

main.go

package main

import (
    "database/sql"
    "log"

    _ "github.com/lib/pq"

    "github.com/gopackx/go-migration/seeder"
    "your-project/seeders"
)

func main() {
    db, err := sql.Open("postgres", "postgres://user:password@localhost:5432/mydb?sslmode=disable")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    runner := seeder.NewRunner(db)

    runner.Register("UserSeeder", &seeders.UserSeeder{})
    runner.Register("PostSeeder", &seeders.PostSeeder{})
    runner.Register("RoleSeeder", &seeders.RoleSeeder{})

    // Run all seeders
    if err := runner.RunAll(); err != nil {
        log.Fatal(err)
    }

    log.Println("All seeders completed successfully!")
}

Running All Seeders

runner.RunAll() executes every registered seeder:

if err := runner.RunAll(); err != nil {
    log.Fatal(err)
}

Registration Order

Seeders run in the order they were registered, unless dependencies override the order.

Sequential Execution

Each seeder's Run method is called one at a time. If a seeder returns an error, execution stops immediately.

Error Handling

RunAll() returns the first error encountered. Seeders that completed before the failure remain applied.

Running a Specific Seeder

Use runner.Run("SeederName") to execute a single seeder by its registered name:

// Run only the UserSeeder
if err := runner.Run("UserSeeder"); err != nil {
    log.Fatal(err)
}

This is useful when you need to re-seed a specific table without running all seeders again.

Complete Example

main.go

package main

import (
    "database/sql"
    "log"
    "os"

    _ "github.com/lib/pq"

    "github.com/gopackx/go-migration/seeder"
    "your-project/seeders"
)

func main() {
    db, err := sql.Open("postgres", "postgres://user:password@localhost:5432/mydb?sslmode=disable")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    runner := seeder.NewRunner(db)

    runner.Register("UserSeeder", &seeders.UserSeeder{})
    runner.Register("RoleSeeder", &seeders.RoleSeeder{})
    runner.Register("PostSeeder", &seeders.PostSeeder{})

    // Check if a specific seeder was requested
    if len(os.Args) > 1 {
        name := os.Args[1]
        log.Printf("Running seeder: %s", name)
        if err := runner.Run(name); err != nil {
            log.Fatal(err)
        }
    } else {
        log.Println("Running all seeders...")
        if err := runner.RunAll(); err != nil {
            log.Fatal(err)
        }
    }

    log.Println("Seeding complete!")
}

The name passed to runner.Run() must match the name used in runner.Register() exactly. If the name doesn't match any registered seeder, an error is returned.

What's Next?

Dependencies — control the execution order of seeders with dependency declarations

Running Seeders

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