diff --git a/utils/mimetypes.go b/utils/mimetypes.go
new file mode 100644
index 0000000..dbf55f1
--- /dev/null
+++ b/utils/mimetypes.go
@@ -0,0 +1,78 @@
+package utils
+
+import "strings"
+
+// Do not depend on the OS for mimetypes.
+// A Windows update screwed us over here and broke all the automatic mime
+// typing via Go in April 2021.
+
+// MimeTypeByExtension returns a mimetype for the given file name extension,
+// which must including the leading dot.
+// If the extension is not known, the call returns with ok=false and,
+// additionally, a default "application/octet-stream" mime type is returned.
+func MimeTypeByExtension(ext string) (mimeType string, ok bool) {
+	mimeType, ok = mimeTypes[strings.ToLower(ext)]
+	if ok {
+		return
+	}
+
+	return defaultMimeType, false
+}
+
+var (
+	defaultMimeType = "application/octet-stream"
+
+	mimeTypes = map[string]string{
+		".7z":    "application/x-7z-compressed",
+		".atom":  "application/atom+xml",
+		".css":   "text/css; charset=utf-8",
+		".csv":   "text/csv; charset=utf-8",
+		".deb":   "application/x-debian-package",
+		".epub":  "application/epub+zip",
+		".es":    "application/ecmascript",
+		".flv":   "video/x-flv",
+		".gif":   "image/gif",
+		".gz":    "application/gzip",
+		".htm":   "text/html; charset=utf-8",
+		".html":  "text/html; charset=utf-8",
+		".jpeg":  "image/jpeg",
+		".jpg":   "image/jpeg",
+		".js":    "text/javascript; charset=utf-8",
+		".json":  "application/json; charset=utf-8",
+		".m3u":   "audio/mpegurl",
+		".m4a":   "audio/mpeg",
+		".md":    "text/markdown; charset=utf-8",
+		".mjs":   "text/javascript; charset=utf-8",
+		".mov":   "video/quicktime",
+		".mp3":   "audio/mpeg",
+		".mp4":   "video/mp4",
+		".mpeg":  "video/mpeg",
+		".mpg":   "video/mpeg",
+		".ogg":   "audio/ogg",
+		".ogv":   "video/ogg",
+		".otf":   "font/otf",
+		".pdf":   "application/pdf",
+		".png":   "image/png",
+		".qt":    "video/quicktime",
+		".rar":   "application/rar",
+		".rtf":   "application/rtf",
+		".svg":   "image/svg+xml",
+		".tar":   "application/x-tar",
+		".tiff":  "image/tiff",
+		".ts":    "video/MP2T",
+		".ttc":   "font/collection",
+		".ttf":   "font/ttf",
+		".txt":   "text/plain; charset=utf-8",
+		".wasm":  "application/wasm",
+		".wav":   "audio/x-wav",
+		".webm":  "video/webm",
+		".webp":  "image/webp",
+		".woff":  "font/woff",
+		".woff2": "font/woff2",
+		".xml":   "text/xml; charset=utf-8",
+		".xz":    "application/x-xz",
+		".yaml":  "application/yaml; charset=utf-8",
+		".yml":   "application/yaml; charset=utf-8",
+		".zip":   "application/zip",
+	}
+)
diff --git a/utils/stablepool.go b/utils/stablepool.go
index 5195b44..147e96c 100644
--- a/utils/stablepool.go
+++ b/utils/stablepool.go
@@ -2,8 +2,6 @@ package utils
 
 import "sync"
 
-// This file is forked from https://github.com/golang/go/blob/bc593eac2dc63d979a575eccb16c7369a5ff81e0/src/sync/once.go.
-
 // A StablePool is a drop-in replacement for sync.Pool that is slower, but
 // predictable.
 // A StablePool is a set of temporary objects that may be individually saved and