fix: use template

internal/gtag/gtag.go

@@ -1,7 +1,6 @@
 package gtag
 
 import (
-	"bytes"
 	"context"
 	"fmt"
 	"go/ast"
@@ -34,42 +33,13 @@ func Generate(ctx context.Context, file, name string) (*GenerateResult, error) {
 	}
 	pkg := f.Name.Name
 
-	buffer := &bytes.Buffer{}
-
-	fmt.Fprintf(buffer, "// Code generated by gtag. DO NOT EDIT.\n")
-	fmt.Fprintf(buffer, "// See: https://github.com/wolfogre/gtag\n\n")
-
-	fmt.Fprintf(buffer, "//go:generate gtag\n")
-
-	fmt.Fprintf(buffer, "package %s\n", pkg)
-
-	fmt.Fprintf(buffer, "import \"reflect\"\n")
-
-	fmt.Fprintf(buffer, "var (\n")
-	fmt.Fprintf(buffer, "valueOf%s = %s{}\n", name, name)
-	fmt.Fprintf(buffer, "typeOf%s = reflect.TypeOf(valueOf%s)\n\n", name, name)
-	for _, field := range fields {
-		fmt.Fprintf(buffer, "_ = valueOfUser.%s\n", field)
-		fmt.Fprintf(buffer, "fieldOf%s%s, _ = typeOf%s.FieldByName(\"%s\")\n", name, field, name, field)
-		fmt.Fprintf(buffer, "tagOf%s%s = fieldOf%s%s.Tag\n\n", name, field, name, field)
-
-	}
-	fmt.Fprintf(buffer, ")\n")
-
-	fmt.Fprintf(buffer, "type %sTags struct {\n", name)
-	for _, field := range fields {
-		fmt.Fprintf(buffer, "\t%s string\n", field)
-	}
-	fmt.Fprintf(buffer, "}\n")
-
-	fmt.Fprintf(buffer, "func (%s) Tags(tag string) %sTags {\n", name, name)
-	fmt.Fprintf(buffer, "return %sTags{\n", name)
-	for _, field := range fields {
-		fmt.Fprintf(buffer, "%s: tagOf%s%s.Get(tag),\n", field, name, field)
+	data := templateData{
+		Package: pkg,
+		Type:    name,
+		Fields:  fields,
 	}
-	fmt.Fprintf(buffer, "}\n}\n")
 
-	src, err := format.Source(buffer.Bytes())
+	src, err := format.Source(execute(data))
 	if err != nil {
 		return nil, err
 	}