feat: use go:embed to embed templates (#1756)

tools/goctl/api/gogen/logic.tpl

@@ -0,0 +1,25 @@
+package {{.pkgName}}
+
+import (
+	{{.imports}}
+)
+
+type {{.logic}} struct {
+	logx.Logger
+	ctx    context.Context
+	svcCtx *svc.ServiceContext
+}
+
+func New{{.logic}}(ctx context.Context, svcCtx *svc.ServiceContext) *{{.logic}} {
+	return &{{.logic}}{
+		Logger: logx.WithContext(ctx),
+		ctx:    ctx,
+		svcCtx: svcCtx,
+	}
+}
+
+func (l *{{.logic}}) {{.function}}({{.request}}) {{.responseType}} {
+	// todo: add your logic here and delete this line
+
+	{{.returnString}}
+}