package main import ( "mime" "strings" "github.com/pkg/errors" ) type mimeDB map[string]string // mimeResolver contains some well-known mime-types and falls back // to mime package to resolve the extension if no internal override // is known for the given mime-type var mimeResolver = mimeDB{ "text/plain": ".txt", // Detected as .asc when using mime package } func (m mimeDB) ExtensionsByType(t string) (string, error) { if v, ok := m[t]; ok { return v, nil } exts, err := mime.ExtensionsByType(t) if err != nil { return "", err } for _, ext := range exts { if !strings.HasPrefix(ext, ".") { continue } return ext, nil } return "", errors.New("no extension found") }