Use Go's //go:embed directive to embed SQL migration files into binary, 1. Put SQL files into migrations/directory; 2. Load files into embed.FS with //go:embed migrations/*.sql; 3. Use sort.Strings() to ensure migration order by file name; 4. Optionally create a schema_migrations table to record applied migrations; 5. Call applyMigrations in main to execute. This method is suitable for simple applications, avoid external dependencies, and is more convenient to deploy.
Using Go's //go:embed directive for SQL migration files is a clean and efficient way to bundle your migration scripts directly into your binary. This avoids relying on external file paths and makes deployment easier. Here's how to do it properly.
? 1. Organize Your Migration Files
Place your SQL migration files in a dedicated directory, such as migrations/ . For example:
migrations/ 0001_init.sql 0002_add_users.sql 0003_add_index.sql
These files should be plain .sql files with the actual SQL statements you want to run.
? 2. Use embed.FS to Embed the Files
In your Go code, use the //go:embed directive to load the SQL files into an embed.FS (file system). Example:
package main
import (
"embed"
"database/sql"
_ "github.com/mattn/go-sqlite3" // or any driver
"log"
"strings"
)
//go:embed migrations/*.sql
var migrationFS embed.FS
func applyMigrations(db *sql.DB) error {
// Read all files in the migrations directory
entries, err := migrationFS.ReadDir("migrations")
if err != nil {
return err
}
for _, entry := range entries {
if entry.IsDir() {
Continue continue
}
// Read the SQL file
content, err := migrationFS.ReadFile("migrations/" entry.Name())
if err != nil {
return err
}
// Execute the SQL
_, err = db.Exec(string(content))
if err != nil {
log.Printf("Failed to execute migration %s: %v", entry.Name(), err)
return err
}
log.Printf("Applied migration: %s", entry.Name())
}
return nil
}? 3. Sort Migrations by Filename (Important!)
Since ReadDir doesn't guarantee order, and migrations must run in sequence, you need to sort them:
import (
"path/filepath"
"sort"
)
// ...
files := make([]string, 0, len(entries))
for _, entry := range entries {
if !entry.IsDir() {
files = append(files, entry.Name())
}
}
// Sort filenames lexicographically (eg, 0001_..., 0002_...)
sort.Strings(files)
for _, filename := range files {
content, err := migrationFS.ReadFile(filepath.Join("migrations", filename))
if err != nil {
return err
}
_, err = db.Exec(string(content))
if err != nil {
return err
}
log.Printf("Applied: %s", filename)
}? Tip: Use zero-padded numbers in filenames (like
0001_...) so they sort correctly.
? 4. Optional: Add Migration Tracking
To avoid re-applying migrations, consider tracking which ones have been applied (eg, in a schema_migrations table):
CREATE TABLE IF NOT EXISTS schema_migrations (
version TEXT PRIMARY KEY,
applied_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);Then, before applying a migration, check if its filename (or version extracted from it) exists in the table.
? 5. Full Example Usage
func main() {
db, err := sql.Open("sqlite3", "./app.db")
if err != nil {
log.Fatal(err)
}
defer db.Close()
if err := applyMigrations(db); err != nil {
log.Fatal("Migration failed:", err)
}
}?? Notes
- The
embedpackage only works with relative paths and literal strings in the//go:embeddirective. - You can't embed files outside the module or use variables.
- Filenames are case-sensitive on some systems.
- Consider using a real migration tool like
migrateorgolang-migrateif you need rollback, versioning, or cloud DB support — butembedis perfect for simple, self-contained apps.
Basically, //go:embed embed.FS gives you a lightweight, dependency-free way to bundle and run SQL migrations. Just keep the filenames ordered and test the flow.
The above is the detailed content of How to use go embed for SQL migration files?. For more information, please follow other related articles on the PHP Chinese website!
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