Update lib/internal/mime.js

Co-authored-by: Nikita Skovoroda <[email protected]>

Author: mertcanaltin

lib/internal/mime.js

@@ -23,7 +23,15 @@ const END_BEGINNING_WHITESPACE = /[^\r\n\t ]|$/;
 const START_ENDING_WHITESPACE = /[\r\n\t ]*$/;
 
 function toASCIILower(str) {
-  return StringPrototypeToLowerCase(str);
+  if (!/[^\x00-\x7f]/.test(str)) return StringPrototypeToLowerCase(str);
+  for (let i = 0; i < str.length; i++) {
+    const char = str[i];
+
+    result += char >= 'A' && char <= 'Z' ?
+      StringPrototypeToLowerCase(char) :
+      char;
+  }
+  return result;
 }
 
 const SOLIDUS = '/';