render.go
func NewTemplateFileSystem(opt RenderOptions, omitData bool) TplFileSystem {
	fs := TplFileSystem{}
	fs.files = make([]TemplateFile, 0, 10)

	// Directories are composed in reverse order because later one overwrites previous ones,
	// so once found, we can directly jump out of the loop.
	dirs := make([]string, 0, len(opt.AppendDirectories)+1)
	for i := len(opt.AppendDirectories) - 1; i >= 0; i-- {
		dirs = append(dirs, opt.AppendDirectories[i])
	}
	dirs = append(dirs, opt.Directory)

	var err error
	for i := range dirs {
		// Skip ones that does not exists for symlink test,
		// but allow non-symlink ones added after start.
		if !com.IsExist(dirs[i]) {
			continue
		}

		dirs[i], err = filepath.EvalSymlinks(dirs[i])
		if err != nil {
			panic("EvalSymlinks(" + dirs[i] + "): " + err.Error())
		}
	}
	lastDir := dirs[len(dirs)-1]

	// We still walk the last (original) directory because it's non-sense we load templates not exist in original directory.
	if err = filepath.Walk(lastDir, func(path string, info os.FileInfo, err error) error {
		r, err := filepath.Rel(lastDir, path)
		if err != nil {
			return err
		}

		ext := GetExt(r)

		for _, extension := range opt.Extensions {
			if ext != extension {
				continue
			}

			var data []byte
			if !omitData {
				// Loop over candidates of directory, break out once found.
				// The file always exists because it's inside the walk function,
				// and read original file is the worst case.
				for i := range dirs {
					path = filepath.Join(dirs[i], r)
					if !com.IsFile(path) {
						continue
					}

					data, err = ioutil.ReadFile(path)
					if err != nil {
						return err
					}
					break
				}
			}

			name := filepath.ToSlash((r[0 : len(r)-len(ext)]))
			fs.files = append(fs.files, NewTplFile(name, data, ext))
		}

		return nil
	}); err != nil {
		panic("NewTemplateFileSystem: " + err.Error())
	}

	return fs
}
func NewTemplateFileSystem(opt RenderOptions, omitData bool) TplFileSystem {
	fs := TplFileSystem{}
	fs.files = make([]TemplateFile, 0, 10)

	// Directories are composed in reverse order because later one overwrites previous ones,
	// so once found, we can directly jump out of the loop.
	dirs := make([]string, 0, len(opt.AppendDirectories)+1)
	for i := len(opt.AppendDirectories) - 1; i >= 0; i-- {
		dirs = append(dirs, opt.AppendDirectories[i])
	}
	dirs = append(dirs, opt.Directory)

	var err error
	for i := range dirs {
		// Skip ones that does not exists for symlink test,
		// but allow non-symlink ones added after start.
		if !com.IsExist(dirs[i]) {
			continue
		}

		dirs[i], err = filepath.EvalSymlinks(dirs[i])
		if err != nil {
			panic("EvalSymlinks(" + dirs[i] + "): " + err.Error())
		}
	}
	lastDir := dirs[len(dirs)-1]

	// We still walk the last (original) directory because it's non-sense we load templates not exist in original directory.
	if err = filepath.Walk(lastDir, func(path string, info os.FileInfo, err error) error {
		r, err := filepath.Rel(lastDir, path)
		if err != nil {
			return err
		}

		ext := GetExt(r)

		for _, extension := range opt.Extensions {
			if ext != extension {
				continue
			}

			var data []byte
			if !omitData {
				// Loop over candidates of directory, break out once found.
				// The file always exists because it's inside the walk function,
				// and read original file is the worst case.
				for i := range dirs {
					path = filepath.Join(dirs[i], r)
					if !com.IsFile(path) {
						continue
					}

					data, err = ioutil.ReadFile(path)
					if err != nil {
						return err
					}
					break
				}
			}

			name := filepath.ToSlash((r[0 : len(r)-len(ext)]))
			fs.files = append(fs.files, NewTplFile(name, data, ext))
		}

		return nil
	}); err != nil {
		panic("NewTemplateFileSystem: " + err.Error())
	}

	return fs
}
// NewTemplateFileSystem creates new template file system with given options.