express can't find static files in build folder. express can serve files in static folder now. but only problem that file path likes <link rel="icon" href="/favicon.ico"/> in index.html it reach res.send('ERROR')

however, when I change favicon and manifest path like <link rel="icon" href="/assets/favicon.ico"/>. it serve file I expected.

• add : I found that if url is localhost//favicon.ico, can access favicon.ico in build folder. (not in assets). only double slash can access build folder, single slash cannot access that. Is my express startpoint localhost/ not localhost?

    server  
    |-server.js
    |-build  
      |-static  
        |-assets  
          |-favicon.ico
          |-manifest.json
        |-index.html  
        |-favicon.ico  
        |-manifest.json  
   

    localhost => return index.html good  
    localhost/index.html, favicon.ico, else... => return ERROR  
    localhost/assets/favicon.ico, manifest.json => return files good
    localhost//index.html, favicon.ico. else... => return files good  

    app.use('/static', express.static(path.join(__dirname, 'build/static')));
    app.use(express.static(path.join(__dirname, 'build')));
    app.use('/*', (req, res) => res.send('ERROR');