fix🐛: embed the seed SQL so migrate works outside the repository root

The seed scripts were read from ./config/ only, so migrating an empty database
failed anywhere that directory was absent, such as a container holding just
the binary and its settings. Embed them and prefer a file on disk when there
is one.

app/admin/models/initdb.go

@@ -3,8 +3,8 @@ package models
 import (
 	"fmt"
 	"go-admin/common/global"
+	"go-admin/config"
 	"gorm.io/gorm"
-	"io/ioutil"
 	"log"
 	"strings"
 )
@@ -44,7 +44,7 @@ func ExecSql(db *gorm.DB, filePath string) error {
 }
 
 func Ioutil(filePath string) (string, error) {
-	if contents, err := ioutil.ReadFile(filePath); err == nil {
+	if contents, err := config.ReadSeed(filePath); err == nil {
 		//因为contents是[]byte类型，直接转换成string类型后会多一行空格,需要使用strings.Replace替换换行符
 		result := strings.Replace(string(contents), "\n", "", 1)
 		fmt.Println("Use ioutil.ReadFile to read a file:", result)

cmd/migrate/migration/models/initdb.go

@@ -3,7 +3,7 @@ package models
 import (
 	"fmt"
 	"go-admin/common/global"
-	"io/ioutil"
+	"go-admin/config"
 	"log"
 	"strings"
 
@@ -61,7 +61,7 @@ func ExecSql(db *gorm.DB, filePath string) error {
 }
 
 func Ioutil(filePath string) (string, error) {
-	if contents, err := ioutil.ReadFile(filePath); err == nil {
+	if contents, err := config.ReadSeed(filePath); err == nil {
 		//因为contents是[]byte类型，直接转换成string类型后会多一行空格,需要使用strings.Replace替换换行符
 		result := strings.Replace(string(contents), "\n", "", 1)
 		fmt.Println("Use ioutil.ReadFile to read a file:", result)

config/seed.go

@@ -0,0 +1,31 @@
+package config
+
+import (
+	"embed"
+	"errors"
+	"io/fs"
+	"os"
+	"path"
+)
+
+// The seed scripts ship inside the binary so a database can be created from
+// wherever the binary runs. They used to be read from ./config/ only, which
+// fails for anything not started from the repository root - a Docker image
+// that carries just the binary and its settings file, for one.
+//
+//go:embed db.sql pg.sql db-begin-mysql.sql db-end-mysql.sql
+var seedFS embed.FS
+
+// ReadSeed returns the seed script at name (e.g. "config/db.sql").
+// A file on disk wins, so a deployment that edits its own copy keeps doing
+// so; the embedded copy is the fallback when there is none.
+func ReadSeed(name string) ([]byte, error) {
+	b, err := os.ReadFile(name)
+	if err == nil || !errors.Is(err, fs.ErrNotExist) {
+		return b, err
+	}
+	if emb, embErr := seedFS.ReadFile(path.Base(name)); embErr == nil {
+		return emb, nil
+	}
+	return nil, err
+}

config/seed_test.go

@@ -0,0 +1,33 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestReadSeedFallsBackToEmbedded(t *testing.T) {
+	// A directory with no config/ in it, as in a container.
+	missing := filepath.Join(t.TempDir(), "config", "db.sql")
+	b, err := ReadSeed(missing)
+	if err != nil || len(b) == 0 {
+		t.Fatalf("embedded fallback: len=%d err=%v", len(b), err)
+	}
+}
+
+func TestReadSeedPrefersDisk(t *testing.T) {
+	p := filepath.Join(t.TempDir(), "db.sql")
+	if err := os.WriteFile(p, []byte("-- mine;"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	b, err := ReadSeed(p)
+	if err != nil || string(b) != "-- mine;" {
+		t.Fatalf("got %q, %v", b, err)
+	}
+}
+
+func TestReadSeedUnknownFileStillErrors(t *testing.T) {
+	if _, err := ReadSeed(filepath.Join(t.TempDir(), "nope.sql")); err == nil {
+		t.Fatal("expected an error for a script that is not embedded")
+	}
+}