Build Zip with goroutines panic with slice bounds out of range with capacity 4096

I'm trying to improve a function to build a Zip by adding goroutines to handle each file that has to be archived.
But it ends up with a panic
panic: runtime error: slice bounds out of range [4126:4096]

The target directory contains 190 files (500 Mo).
I don't really understand what's wrong,
Thank you in advance for your help

The function :

func BuildArchive() error {                                                        
var files []string                                                             
err := filepath.Walk("/tmp/dir-to-zip", func(filePath string, info os.FileInfo, err error) error {
if info.IsDir() {                                                          
return nil                                                             
}                                                                          
if err != nil {                                                            
fmt.Println(err)                                                       
return err                                                             
}                                                                          
files = append(files, filePath)                                            
return nil                                                                 
})                                                                             
if err != nil {                                                                
return err                                                                 
}                                                                              
bundle, err := os.Create("/tmp/archive.zip")                                   
if err != nil {                                                                
return err                                                                 
}                                                                              
bundleWriter := zip.NewWriter(bundle)                                          
var wg sync.WaitGroup                                                          
wg.Add(len(files))                                                             
for _, filePath := range files {                                               
go func(filePath string) {                                                 
defer wg.Done()                                                        
relPath := strings.TrimPrefix(filePath, fmt.Sprintf("%v/", filepath.Dir("/tmp/dir-to-zip")))
bundleFile, err := bundleWriter.Create(relPath)                        
if err != nil {                                                        
fmt.Println(err)                                                   
}                                                                      
fsFile, err := os.Open(filePath)                                       
if err != nil {                                                        
fmt.Println(err)                                                   
}                                                                      
_, err = io.Copy(bundleFile, fsFile)                                   
if err != nil {                                                        
fmt.Println(err)                                                   
}                                                                      
}(filePath)                                                                
}                                                                              
wg.Wait()                                                                      
err = bundleWriter.Close()                                                     
if err != nil {                                                                
return err                                                                 
}                                                                              
return nil                                                                     
} 

The error occurs here :

        _, err = io.Copy(bundleFile, fsFile)                                   
if err != nil {                                                        
fmt.Println(err)                                                   
}   

The stack trace :

goroutine 48 [running]:                                                            
bufio.(*Writer).Write(0xc00002a100, {0xc00041a400?, 0x3d?, 0xc00041a400?})         
/usr/local/go/src/bufio/bufio.go:670 +0x1c8                                    
archive/zip.(*countWriter).Write(0xc00000c138, {0xc00041a400?, 0x3d?, 0x4afa20?})
/usr/local/go/src/archive/zip/writer.go:601 +0x2e                              
io.WriteString({0x4e7538, 0xc00000c138}, {0xc0000212c9, 0x3d})                     
/usr/local/go/src/io/io.go:314 +0x91                                           
archive/zip.writeHeader({0x4e7538, 0xc00000c138}, 0xc000220090)                    
/usr/local/go/src/archive/zip/writer.go:422 +0x5ec                             
archive/zip.(*Writer).CreateHeader(0xc0000760a0, 0xc00021e1b0)                     
/usr/local/go/src/archive/zip/writer.go:378 +0x797                             
archive/zip.(*Writer).Create(0x4e7698?, {0xc0000212c9, 0x3d})                      
/usr/local/go/src/archive/zip/writer.go:223 +0x6c                              
main.BuildArchive.func2({0xc0000212c0, 0x46})                                      
/home/simba/go/src/foobar/main.go:79 +0x1c5                                    
created by main.BuildArchive                                                       
/home/simba/go/src/foobar/main.go:73 +0x5aa                                    
panic: runtime error: slice bounds out of range [:4126] with capacity 4096         
goroutine 6 [running]:                                                             
bufio.(*Writer).Flush(0xc00002a100)                                                
/usr/local/go/src/bufio/bufio.go:634 +0x171                                    
bufio.(*Writer).Write(0xc00002a100, {0xc0001b4200?, 0xc000199b20?, 0xc000199b20?})
/usr/local/go/src/bufio/bufio.go:672 +0xd8                                     
archive/zip.(*countWriter).Write(0xc00000c138, {0xc0001b4200?, 0x0?, 0xc000199b40?})
/usr/local/go/src/archive/zip/writer.go:601 +0x2e                              
archive/zip.(*countWriter).Write(0xc000220018, {0xc0001b4200?, 0xc0001b02c0?, 0xc0001b02f0?})
/usr/local/go/src/archive/zip/writer.go:601 +0x2e                              
compress/flate.(*huffmanBitWriter).write(...)                                      
/usr/local/go/src/compress/flate/huffman_bit_writer.go:136                     
compress/flate.(*huffmanBitWriter).writeCode(0xc0001b41e0?, {0x6000?, 0x22?})   
/usr/local/go/src/compress/flate/huffman_bit_writer.go:347 +0xe5               
compress/flate.(*huffmanBitWriter).writeTokens(0xc0001b41e0, {0xc002558000, 0x4001, 0x403f800000403f?}, {0xc0001aa900, 0x11e, 0x108129000000000f?}, {0xc0001ac100, 0x1e, 0x1e})
/usr/local/go/src/compress/flate/huffman_bit_writer.go:583 +0xb9               
compress/flate.(*huffmanBitWriter).writeBlock(0xc0001b41e0, {0xc002558000?, 0x20?, 0xd79?}, 0x0, {0x0, 0x0, 0x0})
/usr/local/go/src/compress/flate/huffman_bit_writer.go:495 +0x490              
compress/flate.(*compressor).writeBlock(0xc0005a2000, {0xc002558000?, 0xc000032f00?, 0xc000199d28?}, 0x47739b?)
/usr/local/go/src/compress/flate/deflate.go:170 +0x9c                          
compress/flate.(*compressor).deflate(0xc0005a2000)                                 
/usr/local/go/src/compress/flate/deflate.go:509 +0x59b                         
compress/flate.(*compressor).write(0xc0005a2000, {0xc00256a000?, 0x8000, 0xf311b6fd?})
/usr/local/go/src/compress/flate/deflate.go:554 +0x82                          
compress/flate.(*Writer).Write(...)                                                
/usr/local/go/src/compress/flate/deflate.go:712                                
archive/zip.(*pooledFlateWriter).Write(0xc00020c040?, {0xc00256a000?, 0x8000?, 0x4af140?})
/usr/local/go/src/archive/zip/register.go:51 +0xc5                             
archive/zip.(*countWriter).Write(...)                                              
/usr/local/go/src/archive/zip/writer.go:601                                    
archive/zip.(*fileWriter).Write(0xc000222000, {0xc00256a000, 0x8000, 0x8000})   
/usr/local/go/src/archive/zip/writer.go:533 +0x97                              
io.copyBuffer({0x4e7558, 0xc000222000}, {0x4e7678, 0xc0001f8008}, {0x0, 0x0, 0x0})
/usr/local/go/src/io/io.go:428 +0x204                                          
io.Copy(...)                                                                       
/usr/local/go/src/io/io.go:385                                                 
main.BuildArchive.func2({0xc00001c0c0, 0x35})                                      
/home/simba/go/src/foobar/main.go:89 +0x385                                    
created by main.BuildArchive                                                       
/home/simba/go/src/foobar/main.go:73 +0x5aa                                    
exit status 2

zip.Writer is not safe for concurrent use. You launch multiple goroutines, each creating and writing to zip entries (files).

Writer.Create() documents that:

> Create adds a file to the zip file using the provided name. It returns a Writer to which the file contents should be written.
>
> [...] The file's contents must be written to the io.Writer before the next call to Create, CreateHeader, or Close.

You can't create a zip concurrently. io.Writers of each zip entry write to the same underlying file (or to the same io.Writer in general), even if your app doesn't panic or crash, the resulting zip archive will likely be invalid.